function checkMfield(f) {
if(!isNumeric(f.value)) {
	alert("Your membership number must be numeric.")
	return false;
}
else {
	if(f.value.length != 7) { // membership number happens to be 7 chars
	var zeros = '';
	for(var i = 0; i < (7 - f.value.length); i++)
		zeros = zeros+'0';
	f.value = zeros+f.value;
	}
     }
return true;
}
function isNumeric(x) {
var RegExp = /^(-)?(\d*)(\.?)(\d*)$/; // Note: this WILL allow a number that ends in a decimal: -452.
var result = x.match(RegExp);
return result;
}