To enhance cj20n project profile screen

Hello,

I have a requirement in which I need to enhance a particular tab (refer last screenshot) for project profiles in cj20n transaction code. Now, this tab is already customised and available in CJWB function group, screen number 3998. I suppose this is the only tab where we can add our Z fields for cj20n project profiles. also, it is being implemented in CNEX0006 enhancement.

now, I want to replace sub-screen 600 dynamically according to project profiles selected in cj20n transaction code. but, since this screen exit is already implemented, I cannot edit the program and call sub-screen according to my requirement.

can you please suggest me ways how I can achieve my requirement.

CJ20N tab where I want to call different subscreens according to project profiles selected: