select-options in subscreen

Hi people!

I've got a subscreen with an I/O field and a subscreen. In that subscreen I load a select-option, but when I put data on the fields, I realize the I/O field keeps the data but my select-option is 0, there's no data on it. I'm sure the answer must be really simple but I can't find it and it's driving me nuts. Thanks in advance for your help.

Zigor.