Quickbooks - Changing how payment is applied

We need a C# or .Net library that can use QBXML (preferred) or other means of changing how a payment is applied to different invoices. The component should be able to do the following: Given a Payment Transaction Id and an Invoice Transaction Id it should be able to apply the payment to that invoice. After applying the payment it should return a value indicating how much of the payment is left (or a negative number if its an underpayment). You are free to use QBXML 4.0 and higher and this will be for quickbooks enterprise edition. If you feel there is a better and reliable way to acommplish this (perhaps manipulating quickbooks itself by hooking into the windows) then please include that in your bid. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Deliverables must be in ready-to-run condition, as follows (depending on the nature of the deliverables): a) For web sites or other server-side deliverables intended to only ever exist in one place in the Buyer's environment--Deliverables must be installed by the Seller in ready-to-run condition in the Buyer's environment. b) For all others including desktop software or software the buyer intends to distribute: A software installation package that will install the software in ready-to-run condition on the platform(s) specified in this bid request. 3) All deliverables will be considered "work made for hire" under U.S. Copyright law. Buyer will receive exclusive and complete copyrights to all work purchased. (No GPL, GNU, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the buyer on the site per the coder's Seller Legal Agreement). ## Platform Windows, .Net 1.1, Quickbooks, C#