Fundraising plugin

I have the fundraising plugin set up, but the problem I am finding is this plugin requires the IPN to be set to:

And I already have the IPN set to a different url because I am using Gravity Forms to get membership fees and make payments, which needs the IPN set to

I can see there is a way to set the IPN dynamically but not sure how to do this with the plugins.

Ideas on how to make this all work? If not, then I will need to not use the Fundraising plugin.