When Trading in an Off-Lease Vehicle: Rollback the Due Upon Signing to "First Payment + PPSA"

When I have a customer leasing a new vehicle and their trade-in is coming off a lease, the taxes owed on the off-lease trade are put in the Due Upon Signing.

I would like the Due Upon Signing to ONLY be the first payment and the PPSA. I do not want the taxes from the off-lease trade in the Due.

In order to accomplish this, I have to select the Due Upon Signing Rollback in Advanced Lease Options - but this rolls back the Due to 0. I then set the base down payment equivalent to the first payment plus the PPSA. The payment then changes, therefore I would need to change the down payment amount. To find the true amount I would have to calculate it about 3 times and then we are still cents off from matching our credit app.

I would like to be able to put the trade on the deal and have a button to then set the Due Upon Signing to be the first payment and PPSA only.