Hi,
This is pretty "easy" actually.
for each player:
-- build a vector P = ( B-A)
-- set the length of the vector P to your radar radius
-- position the player marker using A+P
now you may also want to check that the player is not within the visiblge area of your radar, so simply do a Min() when setting the length of p, so that if B is closer than the perimeter, it will take that into account at no extra work for you.
Does that make sense?
bye,
Jean