linking parameters

So i posted an issue regarding multileader frames. I got some feedback but nothing that actually works the way that we would have liked.

So i went with plan B!!! To create a block that does basically the same thing as the multileaders. Now this is where it gets interesting.

Because of the callout content i inserted a multi line attribute. All of the callout content needs to be enclosed in a frame. So i just inserted a rectangle with two linear parameters (vertical stretch and horizontal stretch) to allow the user to stretch the frame around the text. So far so good.

But now the leader is posing some what difficult. I added a polar stretch to the leader from the elbow to the arrowhead. Then i added a flip parameter. But what i would like to do is have it so that when the leader passes the flip plane that it would preform the flip. As it is each of these parameters would have to been done separately.

Is there a way to link these two parameters so that when the arrowhead passes the flip plane (which is center of the callout frame) that the leader would flip to the other side of the callout? Tried to chain the two but to no avail.