How to stop excel from updating dates.

So your formula uses TODAY() so it will constantly update as long as the checkbox is true.

you could use a circular reference to prevent updates but would have to change the Excel options to allow circular references (e.g. set iterations  = 1) then

=IF( G7 * (H7=""), TODAY(), H7)

BUT instead I would recommend just get rid of the checkboxes and just use the Date recieved and if there is a date there then it is recieved and if not then it is not.  And add the shortcut to let others know how to easily enter that date (CTRL-;)  so something like:

Date Recieved
  ( CTRL - ; )

and if you don't know, you can use ALT-ENTER to create that line feed inside that cell

Then it is nearly as easy to enter the date as it is to click the box and you don't have to worry about circular references and I would claim less likely to error by people accidentally clicking the wrong box and then no knowing how to or forgetting to undo that and hence having the wrong date listed.