some clarifications:
1. Paul needs a solution for Android.
2. So all tricks with STACKS will not work for him.
3. The HTML-tricks will not work, since they will only alter the ASK and ANSWER Dalog STACKS!
4. Since we can only have ONE window (stack) open and displayed at a time on the mobile platform.
ALL stacks will open FULLSCREEN here and we cannot change this behaviour (yet?)!
I would also recommend to use goups, disguised as dialogs.

Set the layer of the group to TOP before showing, add a semitransparent background (filled graphic or whatever with blendlevel set)
to the group behind your buttons and/or fields and it will look as a dialog box and the user cannot click anywhere on the card but
on the buttons you supply in the group just like a nice custom modal dialog!
Best
Klaus