Formula to correlate varying data in one column to varying data in another column

I hope the question isn't to ambiguous. I really had no Idea how to phrase it.

What I'm looking for is a way to calculate time in between key strokes. So I have this csv file that looks like this:

Time(ms)	Hand Rotation	Left Thumb	Right Thumb	Tapping Finger	Code	Mapped Output
3	A	0	0	0	A000
791	A	0	0	0	A00000	Shift
6563	A	0	0	7	A0070000	a
8841	A	1	0	5	A1050000
9346	A	1	0	2	A102000	e

In Column A I have miliseconds, in Columb G i have the mapped output. I want a way to calculate the time in between each keystroke. Something like

To find the first cell with data in G and get the milliseconds in A I have

Formula:

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Then I would have something like

Formula:

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But then how would I continue to map through the data and get a difference every time there is a new mapped output??

So column A will always have milliseconds in it but column G only contains a char if there was a keystroke at that time.

I honestly don't even have a clue on how to go about building a formula to calculate this. Any help or advice would be SUPER appreciated.

Originally Posted by Chris_SS

Hmmm.. when I implement this i get a #NUM error on the rows that have input. In your example you wrap the function with {} yet when I do that on my Excel it gives me an error. I am working with Excel 2013 Professional Plus

After keying in the formula, change it to an array formula by pressing Ctrl + Shift + Enter