milestone-based outgoing payments

Hi All,

Our client requirement is to link outgoing payments with either milestones or activity confirmations..eg: unless a milestone's reached/activity is confirmed indicating a set of receipts of material and service entries, a payment block or invoice block should not be removed. Upon confirmation of activity or milestone, the payment block should be automatically removed so as to enable vendor payment.. searched forum, but didn't find exactly what i am looking for and the steps to achieve the same..

Request the forum mates to offer some valuable insight and detailed steps..

Thanks in advance,