How do I move origin point/connect tilemaps

I am having a bit of a problem today. Is it possible to move the origin point of a tilmap? (seems like that is the problem, because when I move it with a mouse, it snaps to the wrong position). The red dot seems to be the origin point but I want it to be in the middle, like the green dot.

[attachment=0:3mrej5uf][/attachment:3mrej5uf]

I am also having some problems about how to connect the pieces so that they move together after they are connected. Tried the "pin" solution but could not get it too work exactly the way I wanted. Look at the image to see what I mean.

[attachment=1:3mrej5uf][/attachment:3mrej5uf]

I have considered writing a plugin to do all this, but if anyone know if this has already been done, I will appreciate a link to the specified plugin.

Thanks in advance for your help.

Solved one of my problems, new day new possibilites. The top one was nothing other than a little math problem, and I don't think that there are any origin points on a tilmap. But still need help on question #2.