How to trigger print preview like ME23N ?

Hello,

I got a requirement like in ME23N in the applicatin tool bar Print preview. I have to keep a button in my screen painter and when i click print preview automatically the script has to trigger.

For this i have got the data stored in the table and i have designed the script and its working fine. But my problem is how to call the script automatically when i click prinr preview. Wheather i have to call function 'Transaction' "Txcode" or can any give me the idea for this to achieve?

Thks