You can still put the contents of the "tab" in its own deck different from the deck it is controlling. So card 1 of the tab's Deck shows the normal view of the tab. This card contains the normal view of the graphics. The stimulus to press on the tab is on one or more of the objects in this card. Then card 0 contains graphics for the disabled look for the tab and no stimulus to press on it.
Do you mean you are using a Tab Bar object for the tabs (from the tabbars.dsn models library)? If so, then it is a matter of "catching" the tabSelected event with a control WHEN block and forcing it to change back to the previously selected option. The full capabilities of the Tab Bar object are described in the Altia Design User's Guide, Chapter 6 - Models Libraries, Section 6.6.11 - Tab Bar Object.
If none of this is making sense, you may want to send an email to firstname.lastname@example.org
to ask for more help if you have support for your Altia Design software.