Placing an order using PiBridge

I am fairly new to Amibroker AFL. While going through the code for placing an order
via PiBridge; I want to know if the buy code will be fired each time a buy signal is getting generated during the formation of the bar (say 15-minute).
I want the buy order to get fired only at the end of a bar if there is a buy signal.
For e.g the MACD line may cross while the bar is forming but may not at the end of
the time period. So then I do not want the buy code to be fired.
Also I want to know if there can be a buy popup or dialog so that I can manually OK the placing of order.