Update Data activity using an editable integer

Hi Adobe community

I'm having difficulty with a very specific problem in Campaign Standard. At the end of my workflow I want to do an Update Data activity to update an an attribute in my custom resource with a date stamp that is 'today + 14 days', aka AddDays(GetDate(),14)

The '14 days' is an integer that i want to easily be able to change without interfering with the workflow due to a client's business requirements. As such, I have created a new custom resource called 'Global Configurations'. This schema of this is 'label, integer'. This is published and I have created data within it that looks like: label: exit_time; integer: 14. There are no links in this Global Configurations custom resource.

I want to be able to edit the integer of '14' in this new custom resource to any other number based on my client's business requirements and have the workflow automatically update the last update activity to 'exit_time' = today + x days.

How can i incorporate this attribute into my workflow so that this number can be changed outside the workflow? I want it to be something like AddDays(GetDate(),[attribute='exit_time']) - how do I express this correctly so that the update data activity will respect this?

Hoping what I am describing makes sense.

Cheers

Damien