tick testing multi-pair portfolio strategies

[Mark Lewis]

if i create a custom symbol similar to DXY, but which contains all of the symbols in the expert that i want to test then set the back-tester to test on that custom symbol (making sure the symbols actually tested are hard coded into the algo), will i end up with a compiled time-series of ticks for the ontick() function so that as soon as there is a tick in any one of the pairs within the portfolio, the EA runs the ontick()? This is instead of setting the tester to say EURUSD and only calculating the other pairs in the portfolio when there is a tick in EURUSD or using the ontimer() function.

[Enrique Dangeroux]

I have no experience with custom symbols. But from what i have read, there are some issues with it. 

Another posibility is the OnChartEvent to process ticks from the correct symbol. See https://www.mql5.com/en/articles/234