Here is a simple script that you can assign to a button. I tried it assigned to the side button on my treo 700wx and it works great. If you have AE Button Plus you can assign it to any button.
What this script does is open the mail folders for selection. If tmail isn't active it will launch it first. Before this you had to whip out your stylus to switch folders unless you have WM5 AKU3.0 or later.
Code:
# FolderSwitch.mscr - launches or makes tmail active and sends a
# screen tap to open mail folders.
callTmail = True
current = ActiveProcess()
If ( current eq "tmail.exe" )
callTmail = False
EndIf
If ( callTmail )
Run( "\Windows\tmail.exe" )
Sleep( 5000 )
EndIf
activeWin = ActiveWindow()
MouseClick( activeWin, 10, 10 )