# Days since last enrollment

So from the video at https://www.youtube.com/watch?v=we32kThtuuo. I was able to create what I call “Days Since Last Session Enrollment.”

The formulas generated are as follows:

```````Date of Last Term Session Begin = LASTDATE('WW Registrations'[Session Begin Date] )`

Days Since Last Term Session Begin Date =
IF( ISBLANK( [Date of Last Term Session Begin] ), BLANK(),
VALUE( [Last Term Session Begin Date] - [Date of Last Term Session Begin]))
``````

Everything works but then I thought about something that is critical in higher education as we don’t necessary keep a perpetual customer, at least in the sense of enrollment. So lets say the output for a given student says that the “Days Since Last Term Session Begin Date” is 2,170 at face value I would assume something is wrong but in actuality, there is another piece of the puzzle being that the student might have graduated so there would not be any further Session Begin Dates. I have a graduation file that has a degree conferred date. The common element between all data files is the student ID. I have not yet brought the graduation file into this particular model but can I craft a formula that essentially does the following:

Identify the Days Since Last Term Session Begin Date if the student ID is not present in the graduation file? I truly only want to show Days Since Last Term Session Begin Date if we do not have a record of the student having graduated.

In the model, the Customer Table for me is called the Student Table and WW Registrations is connected to that. I assume I need to add the WW Graduates file and connected it to the Student Table. But then how do I introduce logic into the formula that would filter out any student who is in the WW Graduates file from showing in the visual that would reflect Days Since Last Term Session Begin Date?

I think you pretty much have this, especially around the logic in the model. You definitely need the customer table to have a relationship to the graduation table.

It shouldn’t be too difficult to write some IF logic that says if the student has graduation don’t make that BLANK versus those who aren’t.

I would just set this up in your model and test a few variations. It doesn’t seem that difficult once you have the model set up.