accessing dynamic generated dom element with javascript in IE

I a creating a site for entering tests
the instuctor can add questions whenever he needs and the question and
answer fields are appended with the questions counter

I've created a javascript function to validate the questions
the problem is that it doesn't work in  IE it worked in firefox

this is how I access the fields
for (i=1 ; i<= counter ; i++)
{	
	if ((q = myform.elements["Q_" + i]))
	{

		if ( q.value == "")
		{
	 		str = str + 'enter a question plz'
                }
	}	
              
}
in IE  q is considered undefined!

is there any other option, coz I need the code to work in IE
thank you
aurora





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