Calculating change in cell

[DrLight]

My Real-time Data tool is going to be changing an integer in cell F2 every couple seconds.

I want Cell I2 to measure the change.

When F2 goes from 10->35, I2 should read 25.

Is this possible?

 

[DrLight]

I should add I am brand new to Macros. If this was Java I'd be fine!! Thanks for any help!