Something

<script type="text/javascript" language="JavaScript">
function recalculateDestination_16155_1202292232()
{
			var myRegEx = new RegExp("\d");
	var dimensions = myRegEx.exec("Bonn Black Floor 333 x 333");

	if( dimensions == null ) {
		alert( "Sorry, unable to calculate number of tiles" );
		return;
	}

	var tilearea = dimensions[1] * dimensions[2];
 	document.orderform_16155_1202292232.meters_squared.value = tilearea;
 	document.orderform_16155_1202292232.amount.value = document.orderform_16155_1202292232.meters_squared.value;
}
</script>