no, sorry. I have thought of GetPossibleCount() - but it has to be more specific than that.
On that field >item_in<, there are three values - like "here", "there" and "both".
That field - a comparison - makes sense only for the items in both calculations, so one out of those three possible values has to be selected. That's what the display_condition queries right now.
The issue is, if a selection is made on some comparison, then only the value "both" is selectable at all in that field, so the user would certainly expect to see that field in the detail_table - but as the display_condition is not fulfilled, the field does not show up.
P.S.: Unless (or until) I find some better solution, I will put a textbox with a comment next to the multibox for the selections on that sheet. In the multibox one can see when only one value is selectable as it will be displayed, so the user can easily just click on it in that case.