How to hide conditionally custom fields in screen exit? (CMOD) - abap

Question

My task is to customize the Header Details Screen of the ME33K transaction, the goal is to add a box with new fields that should appear only if the Agreement type is the one I defined by using the transaction SPRO (ex: Agreement type ABC).
I started making an enhancement to that screen by using the CMOD transaction, I created a dummy box and field with some hard-coded input value and it's working fine.
My next step would be to make these new fields appear only if the Agreement is of type ABC, but I cannot find the correct approach.
I tried doing some Screen-Loop programming and deactivating the box and/or fields, but the only ones that get deactivated are the standard ones that exist already, the ones I added with the enhancement are not affected.
EDIT :
The enhancement I used was 'MM06E005'.
I wrote the following Screen-Loop code in the include provided in the 'EXIT_SAPMM06E_006' user exit :
loop at screen.
if screen-name = 'CUSTOM_FIELDS'.
screen-active = 0.
modify screen.
endif.
endloop.

Answer 1

The enhancement MM06E005 refers to the subscreen SAPLXM06 0101, that you have created with a box with all your custom screen fields.
To hide your custom screen fields, you must:
Call a PBO (Process Before Output) module, to be done in the flow logic of your subscreen (the one which contains the screen fields):
PROCESS BEFORE OUTPUT.
...
MODULE modify_screen_field_attributes.
...
PROCESS AFTER INPUT.
...
In the include LXM06O01 (preferrably), do this:
MODULE modify_screen_field_attributes OUTPUT.
LOOP AT SCREEN.
IF screen-name = 'CUSTOM_FIELDS'. " name of one screen field
screen-active = 0. " hide the screen field
MODIFY SCREEN.
ENDIF.
ENDLOOP.
ENDMODULE.