You can make an expert run every number of miliseconds, using infinite while loop in Init(). Look below for an example.
Code:
int init()
{
if (IsExpertEnabled() == true)
{
if (IsTradeAllowed() == true)
{
while (true)
{
//------Your code here---
Sleep(1000);
}
}
}
return(0);
}
int start()
{
return(0);
}
It will run aproximately every second.
Wookey