function countInstances(f, c, open, closed)
{
	var opening = eval('document.'+f+'.'+c+'.value').split(open);
	var closing = eval('document.'+f+'.'+c+'.value').split(closed);
	return opening.length + closing.length - 2;
}

function TAinsert(f, c, text1, text2)
{
	var ta = document.getElementById(c);
	if (document.selection)
	{
		var str = document.selection.createRange().text;
		ta.focus();
		var sel = document.selection.createRange();
		if (text2 != '')
		{
			if (str == '')
			{
				var instances = countInstances(f, c, text1, text2);
				if (instances % 2 != 0)
					sel.text = sel.text + text2;
				else
					sel.text = sel.text + text1;
           		}
           		else
		              sel.text = text1 + sel.text + text2;
	        }
        	else
	           sel.text = sel.text + text1;
	}
	else if (ta.selectionStart | ta.selectionStart == 0)
	{
		if (ta.selectionEnd > ta.value.length)
			ta.selectionEnd = ta.value.length;
		var firstPos = ta.selectionStart;
		var secondPos = ta.selectionEnd+text1.length;
		ta.value=ta.value.slice(0,firstPos)+text1+ta.value.slice(firstPos);
		ta.value=ta.value.slice(0,secondPos)+text2+ta.value.slice(secondPos);
		ta.selectionStart = firstPos+text1.length;
		ta.selectionEnd = secondPos;
		ta.focus();
	}
	else
	{
		var sel = document.f.c;
		var instances = countInstances(f, c, text1, text2);
		if (instances % 2 != 0 && text2 != '')
			sel.value = sel.value + text2;
		else
			sel.value = sel.value + text1;
	}
}