I am re-creating a an app I created in MS-Access.  What I am trying to do is to create an amortization schedule which means I have to work with dates.  Dates seems to be handled differently.

 

 

Here's how I did it in Access.  I had a table the needed periods.  Period ID, Date that would be the month end.  Then I had a decision box to close the period when complete.  So I feel like I want have a table with periods.  Where I maintain the assets, I use a lookup field.

 

The challenge is I am not able to calculate the number of periods.  Is that because I am using a lookup field?