I have several lat/long readings from a GPS device in excel.

I need to calculate the distance between points. How?

For Latitude, I'm thinking
Pi*7900/360*(lat1-lat2)

Longitude must need some sort of correction for latitude, not sure
how.

Once i get lat distance and long distance
sqrt(lat**2 +long**2)

I need to write this all into excel.

Extra credit question.
Is there some way to make this into a excel function so you just give
it the the two pairs of readings?

Karl