function digitvalidation(entered, min, max, alertbox, datatype)
{
with (entered)
{
checkvalue=parseFloat(value);
if (datatype)
{smalldatatype=datatype.toLowerCase();
if (smalldatatype.charAt(0)=="i")
{checkvalue=parseInt(value); if (value.indexOf(".")!=-1) {checkvalue=checkvalue+1}};
}
if ((parseFloat(min)==min && value.length<min) || (parseFloat(max)==max && value.length>max) || value!=checkvalue)
{if (alertbox!="") {alert(alertbox);} return false;}
else {return true;}
}
}

function zipvalidation(thisform)
{
// This function checks the entire form before it is submitted
// Note: This function needs to be customized to fit your form
with (thisform)
{
if (digitvalidation(PostalCode,5,5,"Please enter a valid 5 digit US zip code","I")==false) {PostalCode.focus(); return false;};
}
}