Help Update MID function with additional character based on same value in multiple of 3.

[gargilang]

Hello, I need help with updating below formula to add some characters to make it more unique among themselves. Please see below example in yellow.

Book1
	A	B	C	D
1	Data	Item
2	1_1111_aaa	1111	1111	TRUE
3	2_22222_aaa	22222	22222	TRUE
4	3_22222_bbb	22222	22222	FALSE
5	4_22222_ccc	22222	22222	FALSE
6	5_3333_aaa	3333	3333-1	TRUE
7	6_3333_bbb	3333	3333-1	FALSE
8	7_3333_ccc	3333	3333-1	FALSE
9	8_3333_ddd	3333	3333-2	TRUE
10	9_44444_aaa	44444	44444-1	TRUE
11	10_44444_bbb	44444	44444-1	FALSE
12	11_44444_ccc	44444	44444-1	FALSE
13	12_44444_ddd	44444	44444-2	TRUE
14	13_44444_eee	44444	44444-2	FALSE
15	14_44444_fff	44444	44444-2	FALSE
16	15_44444_ggg	44444	44444-3	TRUE
Sheet1

Cell Formulas
Range	Formula
B2:B16	B2	=SUBSTITUTE(MID(A2,FIND("_",A2,1)+1,5),"_","")
D2:D16	D2	=MOD(COUNTIF($B$2:$B2,B2),3)=1

If the same items is repeated more than 3, than I would need them to be unique among themselves to separate them. The character to differentiate can be anything (-1, -2, -3 or a, b, c). Probably combining the Mod function that I use on the other cell?
I hope it makes sense. Thank you for all the help in advance.

 

[bebo021999]

C2:

=TRIM(MID(SUBSTITUTE(A2,"_",REPT(" ",10)),10,10))&IF(COUNTIF($A$2:$A$16,"*_" &TRIM(MID(SUBSTITUTE(A2,"_",REPT(" ",10)),10,10))&"_*")>3,"-"&INT((COUNTIF($A$2:$A2,"*_" &TRIM(MID(SUBSTITUTE(A2,"_",REPT(" ",10)),10,10))&"_*")-1)/3)+1,"")

 

[gargilang]

C2:

=TRIM(MID(SUBSTITUTE(A2,"_",REPT(" ",10)),10,10))&IF(COUNTIF($A$2:$A$16,"*_" &TRIM(MID(SUBSTITUTE(A2,"_",REPT(" ",10)),10,10))&"_*")>3,"-"&INT((COUNTIF($A$2:$A2,"*_" &TRIM(MID(SUBSTITUTE(A2,"_",REPT(" ",10)),10,10))&"_*")-1)/3)+1,"")

Thank you Sir! I love you from the bottom of my heart!

 

[bebo021999]

Nice to hear it works.
If your data reach several thousand rows, formula may cause PC slow down.
If so, come back and VBA code will be offerred.