Examples: MQL4 Language for Newbies. Introduction - page 2

[honest_knave]

You shouldn't have a semicolon after OnStart()

void OnStart();
{
double AveragePrice = 0.0;
int a = 0;
for(int a = 0; a < Bars; a++)
    AveragePrice += High[a];
MessageBox("AveragePrice= " + AveragePrice, "Average Price");
return(0);
}

[randall nunez]

good job!! 

I learn a lot, thank you