x++, Formating user's input with dot

Hi experts,

I have a question, now i'm working on this new form X, with Datasource Y.
In this form i have a field :
Numberfield : ........(textfield)............
i need to format this numbers in that field so user entered numbers like this :
xxx.xxx.xxx.xx (in form side)
but in the table it will be stored as xxxxxxxxxxx without dot (in table side).
My question is how to call this field? And any idea how to achieve it?
Thanks.