iprocurment account generation / personalization help

We have a requirement to have our iprocurement expense requisitions use a Header level DFF to trigger account generation. I have modified and tested the account generator WF to carry out this charge accounting change. However, when updating the DFF it does not re-trigger the account generator automatically.

Is there a way to have the change of the req header DFF retrigger the account generator? Or some other trigger point?

I have noticed that if you select a new requestor or null the current requestor and re-select the same, after selecting the DFF then the account generator will fire again. If the triggering of the account generator is not possible on DFF change then we may be able to live with defaulting the Requestor to Null. However, I am not having any luck with the OAF personalization for that as well.