Possible to pay invoice from 2 internal bank account?

Hi,

We have a requirement to be able to pay an invoice from 2 different internal bank accounts.  How can this be accomplished?

Right now, we have setup the pay group on the invoice header as the criteria for selecting what bank account to pay from.  The payment templates has selection criteria to select only a certain pay group.  I have tried:

-          I tried to split the payment in the scheduled payments tab of the invoice workbench, and put 1 scheduled payment line on hold. 

-          Then run a payment. (only part of the invoice is paid)

-          Then I was hoping to be able to change the pay group on the invoice header after the first payment is done to use the other pay group