Check field in a select-opton

Hi, is there anyone that can help me to solve this problem?

I have 2 seach field in a report,

Filed 1 and field 2

The user put in a value in field 1, the search in field 2 i dependet of what the user have put in into field 1, so, when the user press PF4 in field 2, different value will show up (dependent of value in field 1).

That is no problem if the user press enter between or run the program but if he/she fill in value in field 1 and then directly press PF4 in field 2, there is no value in the SO-table from field 1.

How to check the value?? Please help...

BR//