Appearance OPTIONS

please could someone help me..
I have a "string" field with appearance="numbers" but the option appears for the user to type ' . ' (dot) and ' , ' (comma) and I wish he couldn't put and dot or comma.. is this possible?

Did you try integer apparences :

yes but it looks like "string" with "numbers"
and "integer" are not compatible.. does not work

I understand. I simply thought you could change your text widget to a decimal or integer one.
Maybe you can let user input . and , and erase it from the string in a following calculate question using translate() function.