Say your raw data in sheet WORK is something like this (columns A:C)
[TABLE="class: grid"]
<tbody>[TR]
[TD="bgcolor: #DCE6F1"][/TD]
[TD="bgcolor: #DCE6F1"]A
[/TD]
[TD="bgcolor: #DCE6F1"]B
[/TD]
[TD="bgcolor: #DCE6F1"]C
[/TD]
[TD="bgcolor: #DCE6F1"]D
[/TD]
[TD="bgcolor: #DCE6F1"]E
[/TD]
[TD="bgcolor: #DCE6F1"]F
[/TD]
[TD="bgcolor: #DCE6F1"]G
[/TD]
[TD="bgcolor: #DCE6F1"]H
[/TD]
[TD="bgcolor: #DCE6F1"]I
[/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]1
[/TD]
[TD]Category
[/TD]
[TD]Subcategory
[/TD]
[TD]Sales Description
[/TD]
[TD][/TD]
[TD]Category Unique
[/TD]
[TD][/TD]
[TD]Cat-Sub Unique
[/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]2
[/TD]
[TD]ABS
[/TD]
[TD]ABS 1-1/2
[/TD]
[TD]1-1/2 ABS PIPE PER FOOT
[/TD]
[TD][/TD]
[TD="bgcolor: #D9D9D9"]ABS
[/TD]
[TD][/TD]
[TD="bgcolor: #B8CCE4"]ABS
[/TD]
[TD="bgcolor: #B8CCE4"]ABS 1-1/2
[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]3
[/TD]
[TD]ABS
[/TD]
[TD]ABS 1-1/2
[/TD]
[TD]1-1/2 ABS FITTING CLEANOUT
[/TD]
[TD][/TD]
[TD="bgcolor: #D9D9D9"]BLACK
[/TD]
[TD][/TD]
[TD="bgcolor: #B8CCE4"]ABS
[/TD]
[TD="bgcolor: #B8CCE4"]ABS 1-1/4
[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]4
[/TD]
[TD]ABS
[/TD]
[TD]ABS 1-1/4
[/TD]
[TD]1-1/4 ABS PIPE PER FOOT
[/TD]
[TD][/TD]
[TD="bgcolor: #D9D9D9"]BRASS
[/TD]
[TD][/TD]
[TD="bgcolor: #B8CCE4"]ABS
[/TD]
[TD="bgcolor: #B8CCE4"]ABS 2
[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]5
[/TD]
[TD]ABS
[/TD]
[TD]ABS 1-1/4
[/TD]
[TD]1-1/4 ABS FITTING CLEANOUT
[/TD]
[TD][/TD]
[TD="bgcolor: #D9D9D9"]BUILDING MATERIALS
[/TD]
[TD][/TD]
[TD="bgcolor: #B8CCE4"]BLACK
[/TD]
[TD="bgcolor: #B8CCE4"]BLACK 1
[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]6
[/TD]
[TD]ABS
[/TD]
[TD]ABS 2
[/TD]
[TD]2 ABS PIPE PER FOOT
[/TD]
[TD][/TD]
[TD="bgcolor: #D9D9D9"]COPPER
[/TD]
[TD][/TD]
[TD="bgcolor: #B8CCE4"]BRASS
[/TD]
[TD="bgcolor: #B8CCE4"]BRASS 1/4
[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]7
[/TD]
[TD]ABS
[/TD]
[TD]ABS 2
[/TD]
[TD]2 ABS FITTING CLEANOUT
[/TD]
[TD][/TD]
[TD="bgcolor: #D9D9D9"]ELECTRICAL
[/TD]
[TD][/TD]
[TD="bgcolor: #B8CCE4"]BUILDING MATERIALS
[/TD]
[TD="bgcolor: #B8CCE4"]HANGARS
[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]8
[/TD]
[TD]BLACK
[/TD]
[TD]BLACK 1
[/TD]
[TD]1 BLACK CAP
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD="bgcolor: #B8CCE4"]COPPER
[/TD]
[TD="bgcolor: #B8CCE4"]COPPER 1-1/2
[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]9
[/TD]
[TD]BLACK
[/TD]
[TD]BLACK 1
[/TD]
[TD]1 BLACK PIPE PER FT
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD="bgcolor: #B8CCE4"]ELECTRICAL
[/TD]
[TD="bgcolor: #B8CCE4"]CONDUIT
[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]10
[/TD]
[TD]BLACK
[/TD]
[TD]BLACK 1
[/TD]
[TD]1 BLACK 90 ELBOW
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]11
[/TD]
[TD]BLACK
[/TD]
[TD]BLACK 1
[/TD]
[TD]1 BLACK COUPLING
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]12
[/TD]
[TD]BRASS
[/TD]
[TD]BRASS 1/4
[/TD]
[TD]1/4 BRASS 45 ELBOW
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]13
[/TD]
[TD]BRASS
[/TD]
[TD]BRASS 1/4
[/TD]
[TD]1/4 BRASS UNION
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]14
[/TD]
[TD]BRASS
[/TD]
[TD]BRASS 1/4
[/TD]
[TD]1/4 BRASS COUPLING
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]15
[/TD]
[TD]BRASS
[/TD]
[TD]BRASS 1/4
[/TD]
[TD]1/4 X 1-1/2 BRASS NIPPLE
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]16
[/TD]
[TD]BUILDING MATERIALS
[/TD]
[TD]HANGARS
[/TD]
[TD]1/2 COPPER SPLIT RING HANGER
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]17
[/TD]
[TD]BUILDING MATERIALS
[/TD]
[TD]HANGARS
[/TD]
[TD]1/2 COPPER SWIVEL RING HANGER
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]18
[/TD]
[TD]BUILDING MATERIALS
[/TD]
[TD]HANGARS
[/TD]
[TD]1/2 UNISTRUT CLAMPS PAIR EI U931
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]19
[/TD]
[TD]COPPER
[/TD]
[TD]COPPER 1-1/2
[/TD]
[TD]1-1/2 X 1-1/4 X 3/4 COPPER TEE
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]20
[/TD]
[TD]COPPER
[/TD]
[TD]COPPER 1-1/2
[/TD]
[TD]1-1/2 X 3/4 X 1-1/4 COPPER TEE
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]21
[/TD]
[TD]COPPER
[/TD]
[TD]COPPER 1-1/2
[/TD]
[TD]1-1/2 X 3/4 X 3/4 COPPER TEE
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]22
[/TD]
[TD]COPPER
[/TD]
[TD]COPPER 1-1/2
[/TD]
[TD]1-1/2 COPPER PIPE TYPE M PER FOOT
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]23
[/TD]
[TD]ELECTRICAL
[/TD]
[TD]CONDUIT
[/TD]
[TD]2 PVC CONDUIT COUPLING
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]24
[/TD]
[TD]ELECTRICAL
[/TD]
[TD]CONDUIT
[/TD]
[TD]1 PVC CONDUIT PIPE PER FOOT
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]25
[/TD]
[TD]ELECTRICAL
[/TD]
[TD]CONDUIT
[/TD]
[TD]1-1/2 PVC CONDUIT PIPE PER FOOT
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD="bgcolor: #DCE6F1"]26
[/TD]
[TD]ELECTRICAL
[/TD]
[TD]CONDUIT
[/TD]
[TD]2 PVC CONDUIT PIPE PER FOOT
[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
</tbody>[/TABLE]
Try to use exactly the same data setup (sheets name, rows and columns) and perform the steps below
First of al:
Create a list of unique categories in column E (gray area) and a list of unique pairs Category - SubCategory in columns G:H (blue area)
You can easily achieve this using Data > Remove Duplicates after copy/paste the entire list of Category in column E and doing the same for the pairs Category-SubCategory,
This done and assuming that the drop-downs will be located in
Sheet1
A2 -> Category
B2 -> SubCategory
C2 -> Description
let's create 3 dynamic named ranges and use them in data validation.
Named range CATEGORY
Formulas > Names Manager > New
Name:CATEGORY
Refers to: =OFFSET(WORK!$E$2,,,COUNTA(WORK!$E:$E)-1)
Select Sheet1 A2
Data Validation > List
=CATEGORY
Do the same for SUBCATEGORY
Name:SUBCATEGORY
Refers to: =OFFSET(INDEX(WORK!$H:$H,MATCH(Sheet1!$A2,WORK!$G:$G,0)),,,COUNTIF(WORK!$G:$G,Sheet1!$A2))
Select Sheet1 B2
Data Validation > List
=SUBCATEGORY
At last... (phew)
Do the same for DESCRIPTION
Name:DESCRIPTION
Refers to: =OFFSET(INDEX(WORK!$C:$C,MATCH(Sheet1!$B2,WORK!$B:$B,0)),,,COUNTIF(WORK!$B:$B,Sheet1!$B2))
Select Sheet1 C2
Data Validation > List
=DESCRIPTION
Hope this helps
M.