Help Create a Program Indicator

Dear Community,
I hope this text finds you well. Kindly help create a program indicator that returns the duration in weeks using the current date (V{current_date}) and the date of surgery (A{Ogx5pUkCK7Y}) as attribute. I have tried to use the formula below but is not working.

d2:weeksBetween (V{current_date}, A{Ogx5pUkCK7Y})

What am I doing wrong.

Please help.

Is the engine showing you that it’s invalid or is it that the engine shows in green color that it’s a working expression but then it doesn’t appear in the form?

I want to create the Program indicator so that I plot on the data visualizer chart. How will you create that Program indicator?

It is green. See the image