How to program a user exit variable in BO

Good day:

I'm having a problem when scheduling an Analysis for Excel report on the BO server.

When I was using Bex Analyzer I used the variable Y_DIA_MAYOR, this is an user exit variable and is filled automatically with the actual date so when the report is programmed to be sent by email the report always has the updated data.

When I create the variant I exclude the user exit variable so it won't be fixed and it can change.

I'm trying to migrate the report to Analysis for Microsoft Excel but when I program it to be sent automatically I don't see any option to exclude the variable and when I run the report the date doesn't change, it always refresh with the same date.

Does anyone know if it's posible to do this in the BO platform?.

Thanks in advance for the help