Moveit - create virtual point in the middle of gripper

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Hi. I am using Moveit2 to plan for my manipulator. Attached to the arm I have a fixed gripper, and i am using other methods to control the gripper (just simple open and closing - no moveit). Right now I am setting the planning goal for the manipulator like this:

arm->setGoal(*msg,"base_link_gripper");

I am using a robotiq 2f gripper. What i would like to do is to create some kind of "virtual link/point" in the middle of the gripper (between the fingers) so that i can set the link in "setGoal" to be this virtual link/point. Then the manipulator would move so my goal pose is exactly between the fingers, and i can use my external open/close method.

Is this possible, and in that case, what is the best way to do this?