Insight Reports Adding Custom Formula on Secondary Subject Area Attributes/Metrics

Dear all,

We would like to apply a filter on the following metrics on in several of our custom Insight reports.

Total Clickthrough
Total Clickthrough Rate
Unique Clickthrough
Unique Clickthrough Rate

We want to exclude the links used in our footers from the calculation of above metrics. To be able to keep the footer links out of the calculation of these metrics, we followed the option of applying a formula based on "Clickthrough Link". However, most of our frequently used reports are using the "Email Analysis by Send Date" as the main subject area. Since the "Clickthrough Link" is an attribute from the "Email Clickthrough" subject area, the system gives an error when we try to apply the formula based on Clickthrough Link attribute.