function altTRcolor(tableId,color1,color2){
	 
	
	var evenColor = (!color1) ? '#CCCCCC': color1;
	var oddColor =  (!color2) ? '#E5E5E5': color2;	
	var myTable = document.getElementById(tableId);
	var numRows = myTable.rows.length;

	for(var i=0; i < numRows; i++){
		var bgColor = (i % 2 == 0) ? evenColor : oddColor;
		myTable.rows[i].style.backgroundColor = bgColor;
	}
}