Lock Date when Signed

Not sure if this combination of requirements is possible. 

I have a date field that automatically updates for a form and cannot be edited.

I want this date field to lock the date in place based on a digital signature block.  I saw a post here https://forums.adobe.com/thread/2302655?q=Lock%20date but this is based on saving the document.

The date field is named  "MyDateField".

Is this possible?

Thanks in advance.

JT