EA: Is it possible to buy in the Strategy Tester using the Open of the bar as the price?


I'm trying to test a simple system historically using strategy tester.

I would like to know if it is possible to open an order using the Open price of the current bar. Reason I want to do it this way is because I don't know where the Bid and Ask price come from historically and since my signal is generated on the previous bar, I'm assuming in most live situations I should be able to buy at the open of the current bar.

so how would I do this in my EA?