progr. question

[fxnew]

I just left Metastock Rt behind to get to know MetaTrader Software, which seems much more flexible.

I'd like to ask simple question:

I have an indicator, which shows a signal(graphic) under certain conditions in the typical form of "if then...else etc."

Now, I implemented the function "PlaySound("alert.wav")" when the (signal-) condition(if then..) mentioned above is true.

The problem is:

How do I program the condition/signal so that it is triggering the acoustic alert only if the condition is true FOR THE LAST BAR(and maybe both for "last Bar-1" and the last bar to confirm etc.)in the chart?

(now the alert is triggered as soon as I add the indicator to the chart window) I'd appreciate any help.