Payment type with multiple target accounts

We have many different cafeteria systems and I would like to track them with different accounts. If I do not set up a default target account in transaction types the button is not availale. If I create 9 different transactions and separate buttons, then the buttons will be to small.
The best vould be if a popup window would appear after I hit the cafeteria vouchers, where I can select the appropriate partner…

Create a new entity type for partners and assign partner to the ticket as an entity. When you do this a single Partner Account payment button (like Customer Account) will assign partner account to Target Account. If needed you can automate it further by creating a popup with ask question action and update ticket entity with Update Ticket Entity action.

Thanks!
The ask question solution could work. I tried to figure it out, spent some hours with it. It is really powerful tool!
I could change the entity with it (as selected in question), I could create a tranaction document wfrom receivables to the target payment accoun (amout set in transaction defaults), but I have the following problem:

I can not figure it out how could I use the amount typed in the payment screen, and how could I show the payment on the ticket?

Thanks: Peter

You can read it with {:NUMBERPAD} tag and update payment screen display with Display Payment Screen action.