[SOLVED] Need help creating VBA code for interpolation

Hi guys,

I'm trying to create an aircraft counter for airplanes that are on ground in the airport.

simple version is attached.

Just need to automate it from the before box to the after box. (attached)

Problem is that I've tried using formulas for 2 days now and I'm out of ideas.

The only thing I can think of is through VBA but I have no idea how to use VBA, I've done basic coding through Matlab and C++ but that's all.