How can I say REV to show another language in the keyboard viewer

[Reinhold Venzl-Schubert]

Hi!

I want to type polish text in a field. I switch the keyboard viewer  
(Mac OS 10.6) to Polish and start writing. Every think works well.
But when I change to another field on my card the keyboard viewer  
switches back to german.

I think I need a script like this:

on focusIn
do field "KBVPo" as "applescript"
end focusIn

The content of field "KBVPo is:

         changeInputLanguage("Polnisch Pro")

          on changeInputLanguage(L)
         	tell application "System Events" to tell process  
"SystemUIServer"
	        	tell (1st menu bar item of menu bar 1 whose value of  
attribute "AXDescription" is "text input")
		        	return {its value, click, click menu 1's menu item L}
		        end tell
	        end tell
          end changeInputLanguage

But it do not works as expected. The same AppleScript works very well  
in the AppleScript Editor.

What is the mistake?
What do I have to change?

Thanks
Reinhold