Dear Christian
e.g. check may be:
http://www.consolut.com/s/sap-ides-zugriff/d/e/doc/E-C1F5_SPECIFICATIONS_MODIFY (I found by hazard only german link but english link should be available as well)
Check:
http://www.se80.co.uk/sapfms/c/c1f5/c1f5_specifications_modify.htm
You need to pay attention here. You need to understand that this function module is used for any activity. Therefore you can update value assignment type of type "B" and "C". In "background" the same table is used "ESTVP). Therefore it is "tricky" how to poupulate the parameter "right" and there is a "tricky" add on to know: The "null" topic. (using CG02 you can maintain lower upper limit but you need not and how SAPsolves this is quite tricky
Furtheron what is "tricky" is the "internal" handling of "values" if you have a component of Type C (check ESTVP table).
I found no special link which is reallyrealted to your topic. You "play2 around
C.B.