[SOLVED] strange Javascript behavior

I have two fields on the Edit page that are sitting in a Tab.

I have this code in my Javascript onload event for the Edit page.

var ctrl = Runner.getControl(pageid, 'homeRegionID');
ctrl.setDisabled();

var ctrl = Runner.getControl(pageid, 'homeEncounterID');
ctrl.setDisabled();

But, they're not disabled. I also tried makeReadonly(), but the results were the same.

I can edit the two fields whether I define them as makeReadonly or setDisabled(). The dropdown boxes for the fields still give me all of the selections.

This should be simple (and probably is), but I cannot see where I've done anything wrong. Do I need to define the tab and make that tab active to access the fields?

I am hoping someone can set me straight.