What do you mean by set?
Basically so that the main window opens at a particular dimension.
Depends a little on the OS and version, less so on the Filemaker version.
The File Options under the File menu has settings for what happens when the database is opened, including running a script.PurposeCreates a new window based on the foreground window. You can create a, a , or a .FormatNew Window[Name: <name of window>; Height: n; Width: n; Top: n; Left: n; Style: Document/Floating Document/Dialog]
Then there are Popup Windows
Assuming Windows is your OS http://www.pcmag.com/article2/0,2817,2339650,00.asp
If you find a better solution, please post it.