DPM and partial authorization

[Matthew]

I'm astounded I can't find any information about this in the forums or elsewhere online. Surely I can't be the only one trying to get partial authorizations working with the Direct Post Method?

I think I could get it to work if I could figure out the following:

1. I can't seem to make the gateway return the amount authorized, and,
2. I can get the split_tender_id fine, but if I try to submit it as a hidden form field for a subsequent transaction, the MD5 authentication fails (I've tried subtracting $1.23 from the amount to see if that made any difference, and it didn't.)

Has anyone successfully gotten DPM to work with partial authorizations?  If so, what's the process?

I'm using PHP, but know enough about a few other languages to pretty much understand solutions written in them.

Thanks,

Matthew

[401KC]

I'd also like to be able to do what the OP describes.

FYI, I haven't tried it with Authorize.net, but I was unsuccessful in my attempt to process this type of transaction with PayPal's PayFlow gateway and their equivalent of DPM (transparent redirect).