Validating Screen Fields in FD32 - BTE 1520

Hello everyone,

I have a requirement to make various checks before saving in FD32. For example I want to make sure that KNKK-DBEKR will be less than or equal to KNKK-KLIMK.

I have searched SCN and I have implemented BTE 1520 (you can see an example thread here).

My problem is that while in BTE 1520 I don't have the screen fields available (or at least I don't know how to make them available to my function module).

Has anyone done something similar?

Thank you in advance.