<script language="Javascript">
function trim(thisString){
	var newString = thisString;
	while (newString.charCodeAt(0) < 33)
	{
		newString = newString.substring(1,newString.length);
	}
	
	while (newString.charCodeAt(newString.length - 1) < 33)
	{
		newString = newString.substring(0, newString.length - 1);
	}
	return newString;
}

// Validate that a list of fields contain a value (leading and traling spaces are removed)
// First paramter: the form reference.  If your form name is "ServiceForm", then pass "document.ServiceForm"
// Second Parameter: A pipe delimited list of field names (case senastive)
// Third Parameter: A pipe delimited list of field descriptions
//
function ValidateRequiredFields(thisform,Fields,Desc)
{
	var tmpVal='';
	var FieldArray=new Array();
	var DescArray=new Array();
	var tmp=0;
	// Create array for Field list
	tmpVal=Fields;
	do
	{
		tmp=tmpVal.indexOf('|');
		if (tmp == -1)
		{
			if (tmpVal != '')
			{
				FieldArray[FieldArray.length]=tmpVal;
				tmpVal='';
			}
		} else {
			FieldArray[FieldArray.length]=tmpVal.substring(0,tmp);
			tmpVal=tmpVal.substring(tmp + 1);
		}
	}
	while (tmpVal != '');
	// Create array for Desc list
	tmpVal=Desc;
	do
	{
		tmp=tmpVal.indexOf('|');
		if (tmp == -1)
		{
			if (tmpVal != '')
			{
				DescArray[DescArray.length]=tmpVal;
				tmpVal='';
			}
		} else {
			DescArray[DescArray.length]=tmpVal.substring(0,tmp);
			tmpVal=tmpVal.substring(tmp + 1);
		}
	}
	while (tmpVal != '');
	// Check to see if passed strings are of equal length
	if (FieldArray.length != DescArray.length)
	{
		alert('Fatal error: ValidateRequiredFields - Passed lists do not have the same length');
		return false;
	}
	// Validate fields
	for (i=0; i < DescArray.length; i++)
	{
		eval('tmpVal=thisform.' + FieldArray[i] + '.value');
		if (trim(tmpVal) == '')
		{
			alert(DescArray[i] + ' is required.');
			eval('thisform.' + FieldArray[i] + '.focus()');
			return false;
		}
	}
	return true;
}

function SubmitForm()
{
	if (!ValidateRequiredFields(document.Test,'FirstName|LastName','First Name|Last Name')) return false;
	alert('All is okay!');
}
</script>

<form name="Test">
First Name: <input type="Text" name="FirstName" value=""><br>
Last Name: <input type="Text" name="LastName" value=""><br>
<input type="Button" value="Go!" onClick="SubmitForm()">
</form>