This method is used in the processing page to trigger a client-side function from the server,
after the processing is over.
It is available only when the callback is made asynchronously.
You can have unlimited number of ExecOnLoad methods, and as a parameter
Here is a short example:
public string onClick(int myInt)
// ExecOnLoad examples
// return the number received as argument multiplied by 10
return myInt * 10;
See also ExecOnLoad example