Multiple selection of Material in CS15

Hello Experts,

I have a requirement for the transaction CS15 which is used for single level where used list.

Currently, we can enter only single material on the first screen. Now the client needs to enter Multiple selection for material.

For this, I copied CS15 transaction to ZCS15 and the program to Zprogram. As this is a standard code and is a dnpro screen, I am not pretty sure how I can continue on this requirement. I have seen few other posts mentioning to use "CS_WHERE_USED_MAT" FM but not sure how the screen can be change with multiple selection.

Any inputs on the logic is highly appreciated and rewarded with points.

Thanks,

Sandy