[WD] How to change a TAB Pane state at runtime

Hello to all

It seem to be a stupid question, but i didn't find anything on the online help.

My scenario:
Depending on a choice, i would set a pane in a Tab control to "grayed".
How to do it at runtime?

Tab_Period..Pane[1]..state=grayed     // does not work!!!!

Thanks in advance
Gianni