Drawing curved lines

Very simple question but its driving me mad.
I need to draw a curved line using timeline tweens.
If it was a straight line it would be easy with a short line then further along a longer line and a shape tween in the middle, but curved ?

I have an exampled of what I need to do.

Click on one of the locations on the map.

http://www.lsgroup.co.uk/group.html

I’m sure this is simple