use the Filter ( ) function in an auto-enter calculation for that field, something like:
Filter ( Self ; 1234567890 )
If I want to filter (-) how the calculation would be? I tried to do it but I got some error.
Use this expression as an auto-entered calculation. Clear the "do not replace existing value..." option when you set it up.
THis autmoatically removes all but the numeric digits, so it becomes a self correcting field.
Thanks to raybaudi and PhilModJunk. Now It's working :)