Capturing a snapshot of a field value

[bosteen]

I'm sure there is a way to do this, but I'm striking out. I'm relatively new to FM and at best a novice. I have a schedule. Within the schedule is a field called Class Status. This is a text field with a dropdown where the user selects the status. I have another field called Students. It is a number field where the user enters a quantity. Lastly I have another field called Student Count at Confirmation. I'm looking for that field to capture the data in Students when Class Status is changed to a specific value "Confirmed". I don't want it to change with any subsequent changes to the Students field. In other words, to take a snapshot of the Students field when the Class Status field changes to "Confirmed". The ultimate intent is to be able to compare the Student Count at Confirmation and Students fields at a later date to see how many students were added between the time the class confirms and it is run. I've gotten some suggestions previously but must not understand how to do this. In the Student Count at Confirmation field I've used:

 

If(Class Status = "Confirmed"; Students)

 

However, if under the field options, the "Do not replace existing value of field (if any)" is checked, it doesn't return a value to this field when Class Status is changed to "Confirmed". If left unchecked, it will return a value, but it continues to change as the Student field is changed.

 

Is there a way to do this and if so, can someone provide some simple novice-level instructions? So far, I've expended my limited knowledge.

[Fitch]

Uncheck "do not replace" and make this your auto-enter calc:

 

Case( class status = "confirmed" ; students ; Self )

 

Another option would be to use a script trigger on the status field. But that has its own pitfalls.

[bosteen]

Thank you very much. It worked, but only with "do not replace" checked. With it unchecked, it continued to update. Thanks again!