omegabeta,
One way is to break your elements into four separate text fields.
Assuming your numbers set the max field lengths then set the <input type="text" maxlength="3"> or whatever it is.
You could use vbscript or javascript to test the field for numbers with the mouseout event as an example to test it.
You could display/insert the appropriate periods or comma's between the appropriate <input type="text">
<input type="text" name="f1" maxlength="3">.<input type="text" name="f2" maxlength="3">.<input type="text" name="f3" maxlength="3">,<input type="text" name="f4" maxlength="2">
There might be a way to do this as an ActiveX COM or maybe .HTA, but that is out of my league.
The other alternative is to use the onSubmit or onMouseOut to trigger appropriate validations.
BTW, with Javascript you could test the # char's and jump the user to the next field, trigger the onMouseOut to do validation, which I would use regex. Simpler to do and maintain. Also, Javascript is supported by most browsers, VBScript only on IE.
HTH
DougCranston