Update nth column based on entries from column A,B and C

[RickSorkin]

I am working on a utility and almost completed it.. With the utility I am generating Excel/CSV file with dummy data for my application.
On the file which will be generated, I have Product code(ex: CIDR, HQTC) in column "A" , then in "B" I have dept Id, in "C" I have positions.
So if
CIDR found in column A then search for common dpdt id in column B suppose 100001, now if in Column C we have M,E,S(implying M,E,S belong to same dept)

So below table as reference If CIDR found in A, then

CIDR -->100001-->M, E, --> then update D with 4 for all rows where 100001 is found
Similarly if CIDR -->100002-->M, E--> the update 2 where 100002 is found
if CIDR-->100003-->M--> the update 1 where 100003 is found
or if CIDR-->100004-->M, S--> the update 3 where 100004 is found

Refer sample data:

CIDR	100001	M	4​
CIDR	100001	E	4​
CIDR	100001	S	4​
CIDR	100002	M	2​
CIDR	100002	E	2​
CIDR	100003	M	1​
CIDR	100004	M	3​
CIDR	100004	S	3​
HQTC	100001	M	1​

Any help or approach to handle this.