Hi Kathy,
Your requirements remind me of our As Soon As Impossible blog post, which focuses on "accelerating" a Project plan by setting dependent Task Planned Start Dates to match their Handoff Dates, which get filled in once their Predecessors Actual Completion Date(s) appear (the Handoff Date matching that same Actual Completion Date, "handing off" the momentum of the Project completion to that dependent Task.
In your case, the norm is that the Predecessors (i.e. the Tasks that track the Custom Forms coming back) are late, so you'd then be moving the dependent Task's Planned Completion Date "out", but the concept is the same. You could do so manually, by reporting on those (such) dependent Tasks whose Handoff Date is Not Blank and does not match its Planned Start Date and then copy/pasting the Handoff Date into the Planned Start Date; or if there's enough data that it's warranted, automate that update using (for example) our UberCalc solution.
Regards,
Doug