[MDL] Determining OptionButton SubItem widths

I've got a "blank" (i.e. no SubItems) OptionButton definition in my resource file. I "insert" items dynamically using mdlDialog_optionButtonInsertItem(). When the OptionButton is displayed in the dialog, it contains the entries, but the DialogItem's "width" is zero (I have it set to 0 in the SExtent struct).

1.Is there any way to determine the "width" of a SubItem when inserted into the OptionButton? Just multiply the number of characters times some value (assuming fixed width font)?

2.If a width CAN be determined, is it possible to update the SExtent of the OptionButton so when it open, the "width" is set properly and you can see the entries?

Bruce