Enhancemet for ME22N before me22n transaction executes.

Hi frndz,

my requirement is if user executes me22n then some badi or exit should be trigger because to validate the PO. For example if PO doc date and current date difference is 25 days then all the line items of PO should set with deletion indicator. So i need a badi or user exit to fulfill my requirement before me22n screen displays....I mean if user runs a transaction ME22N then PO line items should hold with deletion indicator if number of difference days are 25.

Thanks in advance.