Advanced payment towards expense report

Hi;

Is there a way, or best practice of how to deal with advanced payment made to employee to be deducted from his/her next expense report? Making a separate list and just "remember" to deduct when expense report is submitted is obviously not the best solution. Any suggestions for better way to deal with it?

I tried using the "Advance to apply" field on the expense report, but this is used only for expenses on the same expense report record. If there are not enough expenses on that record to cover the advance, it will be zeroed out. Also no option to save expense report with negative amount. Here is where I am pretty much stuck and would appreciate other ideas.