set points

hello,

i want to make a couple of points on the XY plane.
I set a starting point1. And an interval (-5,+5). I create a random vector1 on XY in this interval.
The point2 is created by the vector1 from point1. Than i want to calculate the middlepoint from point 1 and 2. This is my new starting point S1. The point 3 is created by another random vector 2 from S1. Calculate the middlepoint for 1,2,3 and set this as startpoint S2. From this create point4 with vector3. Calculate the middlepoint again for point 1,2,3,4 and set as startpoint S3. From S3 create point5 and so on.

If anybody could help?
thanks