Recording the date of a specific update and locking that date?

Greetings SMARTsheeters...

Not sure if what I'd like to do is possible in SMARTsheet, but here goes...

I'm working on a SMARTsheet that receives data adds and modifications from SMARTforms and autoupdate email requests.  There will be various users entering and modifying the data in the SMARTsheet adhoc through these forms and automated alerts to identify any changes in the plan.  We have a team of gatekeepers that will review all of the updates/submissions and approve them.  I'm trying to figure out a way to identify if a row's last change has been approved or if the row is in need of an approval and then (if possible) build some conditional formatting around the cells that have changed and require review/approval.

Initially, I was thinking to capture the approval action via a checkbox and writing the date/time stamp of that action to a last approved date field and clearing the checkboxes somehow when another edit was made.  The Today() funciton could work there, but there is no way to lock the date and it would continue to be a moving target each day...additionally, I don't see a way to automatically clear out the approved checkboxes after a new update is made or the approval is captured.

I'm thinking this might be possible if I somehow manage the approvals through a report where the approval action is captured on a different sheet so I can compare the last modification dates between sheets, but I'm not sure how I could dynamically capture new row adds to the sheet that would manage the approvals...since my forms create new rows upon submission.

Any and all advice on how to handle this kind of situation is more than appreciated!!!