Filtering Phone Number by exact character count

I need to filter leads based on our contact center's ability to handle the lead. The autodialer system can only dial number in the US and Canada without extensions. However, I do not want to limit the character length on forms - we get a small number of valid international inquiries that must be handled outside of the contact center flow. Is there a way to filter for exact character count, in this case 10 characters? I'm already filtering for "does not contain = x, +". This captures most, but not all, of the entries we are trying to filter.

The alternative seems to be separate extension and international code fields on the forms, which I'd like to avoid if at all possible.