Hi,
We can add a validation using the custom patterns so that if the user enters the wrong format (other than SSN) you can let the user to enter correct format by showing a screen tip.
For this follow the below steps.
1. Go to data validation of the text box.
2. Click Add. Select the text box field in the first drop down, does not match pattern in second drop down and select social security number from the standard patterns. Click ok.
3. Write the screen tip that you want to display to the user when he enters wrong format.