Vendor down payment adjustment check in MIRO

Hello,

Could you please help in finding a solution that while posing MIRO document if the is down payment against and down payment is there for say 100, user should not be able to reduce the amount in adjustment line under "Down Payment clearing" tab from less than 100. For example, if user changes 100 to say 99, an error should displayed and should be allowed to adjust full amount i.e. 100.

thanks