Custom Field Number Format

We have added a custom field in the "Potentials" module for tracking project numbers. The field is setup as a number. It is limited to 9 digits and it must be a whole number. Our typical format is 12345.0001 which cannot be accepted because of length and also the decimal point. Can I change this?

Maybe as a work-around I can place the sub-number .0001 in a second field adjacent to the first and connect them somehow?

Eventually we would like to add a custom module to track and sort by project number .

Thank you in advance. Help is greatly appreciated.