Help! I have no idea how to write this calculation!

I need to find out the number of days a student was with us.

Students have a

Start Date

Exit Date

Most Current Exit Date

They may exit and reenter several times during the year and can be gone for days, weeks or months at a time.

Can anyone help me with this?

Thanks!

Hi,

can you lay out a few scenarios for us please? Like the simplest and the most complex - and how you'd solve them on paper. Thanks.