I am in the process of writing a formula for linear interpolation and I have no idea on how to begin.

My data consists of a number of latitude and longtitude points and I want to interpolate data every 50 feet between my 2 ponts and get the latitude and longitude of those points.

I have Lat 1, Long 1 & Lat 2, Long 2

I need help writing a formula to do so

Thanks