Converting unfilled limit orders to market orders

Does anyone have experience with the "convert unfilled limit order to market order" function in Multicharts?

Its hard to understand what it's doing sometimes...
Sometimes it seems to cancel the order instead of converting to market -
other times its changing the bid continuously until it eventually puts in a market order...

I suspect the bid changing is to do with the fact that it is getting new buy orders from the code each time the signal is rerun (every 3 seconds or so?) and it is overriding the original order.
So if that is the case, does anyone know of a way to tell it to stick with the first order it receives and then just convert that one to market if it is not filled?

Thanks,
Todd