Format of SSN field - US version

Is it possible to format the SSN field to leave out the dashes? The reason I ask is that we removed all SSNs some years back and instead use that field (renamed) for Student ID numbers for our alumni. The problem is that our SID are also 9 digits so I've been appending a leading zero to eliminate the dashes. That works, but I wondered if there was an easier solution - i.e. changing the format of the field.

Thanks!