Hi,
You can use multiple validation.
You will need to define groups of all the values that contain A, B, and C separately and name them anything like AGROUP, BGROUP, CGROUP, etc.
So, in this case, AGROUP will contain values such as A10, A1010, A1014, etc.
Put the following list validation in cell B1 and copy-paste it to all the required cells from B to F column:
=INDIRECT(CONCATENATE($A1,"GROUP"))
Now if you select A in the first column, you will only have the options that have A in it to put in the cells in columns B to F.
Refer the attached file.
--Karan--
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