regarding the PopUp Pro plugin on a multisite

I have a multisite, with the Blog Templates. I am trying to configure the PopUp Pro plugin, so that it works on all new blogs on my network. I have created a popup on my template blog that i want to direct the user to a specific page. How can i type in the url so that when they click the call to action button, it goes to that blogs page.

For example: Call to action button says "Continue"

url= /special-offer/

instead of going to http://www.maindomain.com/BLOG/special-offer/

it redirections to http://www.maindomain.com/special-offer/

Is there something i can type into this field to take the visitor to the blog's /special-offer/ page.

I know I can type in the /name-of-the-blog/special-offer/ but then when new blogs are created, it will have my templates blog name in that spot.

Alternately, the special offer is received when doing the blog subscription. I tried using a short code in the popup for the jetpack blog subscription, but it doesn't work.

If anybody can help me out with this, i'd appreciate it.

Please advise,

Jonathan