A related question is whether MF Pro will always submit a proper price regardless of the result of an expression. I seem to recall that it does but cannot find it in the Help file.
For example, say the price is calculated by the trigger as follows:
(back_price+lay_price)/2
and the prices are 2.98 and 3.25 respectively. The result is 3.115. Will MF Pro place the bet at the next closest price, i.e. at 3.10?