Need to bulk create PWDM transmittals and update them later

We need to bulk create PWDM transmittals from a list before we have the scheduled date for each transmittal. We need to go back and revise the created transmittal with the actual dates once the schedule is updated. I see New-PWDMTransmittal can be used to create a transmittal with blank due dates but I do not see a way to revise the due dates or recalculate them at a later time. Any advice?