Another alternative is you can click to allow on account amounts and book this way. But then it doesnt have the same tracking options as you do with a prepayment number. Might this work for your customer?
I would like to know what BackgroundHALShouldPause does, and how to use it. While it's listed in the HAL Primitives report, it is not used in source code and it doesn't appear in the LMS HAL...