PO release Change event control

Hi All ,

i have  two scenarios one is purchase order release and second is when any one changes the 'po' a notification mail to be sent for that standard event CHANGE  is used for triggering workflow and send mail , made an entry in SWETYPV AND SWEC (on change) . when any changes workflow is triggering working fine

During the Po release when a approver clicks on release / cancels / reject / actions Cjange event is triggering which starts the new workflow and send mails to the persons belonged to it ..

here when release cancels terminating events are triggered along with changed event every time ..

how to control change event when any user clicks on release only release action should be done ..

Here PO workflow copy of standard one .

Thanks And Regards

Sandeep Chennoju