Need to set cash account based on payment method

Summary:

Does anyone know if it is not possible to change the cash account on a AP payment?

Content (required):

We have a business need to set the cash account to a different account that is set on the bank account based on the payment method. We tried creating a SLA based on Payment Method Type. However, when we assign this to the cash account in the Account Method it does not pull the new account. To verify that the rule works, we then assign the rule to the cash clearing and when we created the payment the cash clearing account pulled the new account.