Take a look at the Customizing ArcPad Help file under the ArcPad programs folder, i.e. "C:\Program Files (x86)\ArcGIS\ArcPad10.0\Developer\Help\ArcPadStudio.chm".
In the contents tab, locate "ArcPad Object Model Reference", then "Form Object", and Mode property.
Is that what you're looking for?
Hope this helps,
Kyle