I usually use a layout to create the custom dialog when I can't use a custom dialog like the simple dialog by 24U. I create merge variables on the layout and fill them with info. The only thing i can't center it in a new window neither on the iPad and most likely nit in IWP either. I also stay away from IWP like the plague now.
agnes b. riley . filemaker and web development
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On occasion, I've used tab panels (named, so they can be scripted to display). For your "dialog", just go to the second tab. Upon clicking "continue" or something, finish your script and return to the first tab. You can hide the tabs from being "clicked" by overlaying another tab panel (one tab - just the height of the tab only) and make it as wide as the other two. This works in IWP.
With regard to the Freeze Window question: You can omit non-compatible script steps (like Freeze Window) by enclosing them in an If statement using the Get ( ApplicationVersion ) function, like this:
If [ not PatternCount ( Get ( ApplicationVersion ) ; "Web" ) ]