Numeric pointer delta via functional module

Hi all.

I have a generic extractor based on the view. Now I need to implement delta mechanism. The only variant I can use is numeric pointer (view doesn't contain timestamps and date does not satisfy my conditions). But the field i'm going to use is of CHAR type so generic delta doesn't work out.

I decided to write a functional module and the problem is that I don't know with what value should I compare values in my field i.e. how to understand what records are new and extract them?

Thanks in advance.