Comparision of points

[odd hogstad]

I have this model:

class MyPoint(models.Model):
point = models.PointField(null=True,blank=True)

If I have two instances of this model, point1 and point2 and a
distance d=Distance(km=5). What is the best way to determine wether
point1 is within the distance d of point2?

Thanks!

Odd-R.