Add group based on user attribute

Does anyone have the beginnings of a powershell script.  

During user create I have to populate the orgunit with a value.  Based on that value I have to add it to a group.

For example if

orgunit = 1 or 2 and to group A

orgunit = 3 or 4 and to group B

orgunit = 5 or 6 and to group C

This goes on....

I would use the built in policy automatically adds or removed specified objects from specified groups but these will change, and you have to double click on them to find out which one goes where.