Hiya,

No probs. You need to go to "Window->Animation Editors->Expression Editor"

Next, give the expression a name in the "Expression Name" field and click "New Expression"

Type in (or copy an paste) the expression in the "Expression" box...and click "Create"

You need to change the "Object_L" etc. for whatever your object is called. So, if you have say two spaceships called "ship1" and "ship2" with a planet in the middle, your first part of the expression would look something like...

planet.tx=(ship1.tx + ship2.tx)/2;

same goes for translate y

planet.ty=(ship1.ty + ship2.ty)/2;

Move one of the outside objects and your centre object will more with it.

I've attached a snapshot.

-Jacques