How do I calculate distances between postcodes

I have latitude and longitude co-ordinates for UK postcodes.

E.g. For postcode 1 - cell c2 latitude d2 Longitude
For postcode 2 - cell c3 latitude d3 longitude

Does anyone know of a formula I can use to estimate the distance between two postcodes?

I do not use VBA.

Thanks in advance for your help v. much appreciated

The formula to give the distance in miles is

=6371*ACOS(COS(RADIANS(90-C2))*COS(RADIANS(90-C3))+SIN(RADIANS(90-C2))*SIN(RADIANS(90-C3))*COS(RADIANS(D2-D3)))/1.609

Point1 Latitude 53.430094 Longitude -2.961845
Point2 Latitude 53.462887 Longitude -2.291808
gave me Distance = 27.67Miles

PS - I did not work this out myself. Picked it up somewhere on the internet and filed it away for moments like these!