I have a trade proposal ready that would put me over budget, but if the recipient accepts I am prepared to transfer money from my prospect payroll, of which I have plenty, to get me back in the black.  Will doing it this way work, so that am under budget when the trade is completed, or do I have to be under budget when the trade is accepted?  Thanks much.

I'm 99% sure it's when the trade is completed... IIRC from the warning you get when you submit the trade.

Thanks Iain, as always.