Time Stamp for Start of New Entry

Hi All, 

I am trying to figure out if it is possible to create a time stamp for when a New Form is Started. 
The Created Date provides me when the form was completed. What I am trying to get is the duration of time it took to fill out the form. 

The couple things I have tried is not calculating correctly. 
Formula triggering a change in a field to provide  a time stamp
Letting the person filling out the form trigger it by filling the form out and the trigger dependant on the change in field. 
Both of these did not end up working as the time stamps continue to only update a few seconds before the submit button. 
I tested it by submitting an entry 30 min after opening the form. 

Any help is greatly appreciated!

Thanky ou

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Amber Anderson
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