Sebastian:

I appreciated the additional information you provided.

Combo boxes, I think, are great if your pick lists are offer less than 25 choices. One alternative that I like (when their may be many, many more choices than 25), is to have a command button next to your "condition" textbox. This command button when clicked brings up a pick list dialog form. The user can navigate through the list box using the scroll bar (or incremental search if the user is fast at the keyboard). This goes very fast, even when there are hundreds of records to chose from (of course it helps if the conditions are listed in some intuitive order)!

When the user double-clicks on a row in the pick list dialog form, the dialog closes and the user's selection is automatically inserted into the "condition" textbox. Also, if the command button next to your condition textbox uses the 'small binoculars' bitmap, it looks really sharp!