Create matrix with values based on dropdown list

Hello Experts,

I have created a matrix with multiple columns and measures in values. This means, I have multiple sub columns in every parent column of the matrix. Eg: Column 1 has Sub column A, B, C,D. Similarly Column 2 has A,B,C,D and so on where A and B are Columns from some table and C, D are measures created using formulas.

Can I have these subcolumns selected using a drop down?

So that my matrix has only Column 1,2,3,4..... and values I can select from the dropdown which has option to select from A,B,C,D ?

Thanks in advance.