Need to display custom message when Vendor clicked on process bid in SRM 5.0 ITS screen

Dear All..

how to display custom message when Vendor clicked on process bid in SRM 5.0 ITS screen ,

we are trying to add logic on BBPGLOBAL 300 in ITS BBPSTART , which is not triggering

before list display.

Requirement is to display custom message when vendor clicked on process bid before displaying Bid

list, need to display custom message.

Thanks,

Krishna