This function returns the bar number according to the currency and datetime being passed in. This function is good for trailing stop methods that need to know when the entry of the bar occurred.

getOpenBar.mq4

int getOpenBar( string sym, datetime openTime ) {
	// each bar has the opening time at the start of the bar
	// eg if openTime is 12:01PM we will know at 4:00PM (when the
	// bar is greater than the opening time of trade)
	for ( int i = 0; i < Bars; i++ ) {
		if ( openTime >= Time[i] ) {
			return( i );
		}
	}
}