An auto-enter calculation should do the trick:
If ( Not IsEmpty ( CheckBoxField ) ; Get ( AccountName ) & " " & Get ( CurrentTimeStamp) ; "" )
You might consider two such fields, one for the account name and one for the timestamp as that makes the entered data easier to work with. There's an option that goes with auto-entered calculations: "Do not replace existing value". You can try this out with the option selected and de-selected to see which works better for you in this case.
You can use access privileges to keep users with the wrong privilege set from editing records that have been "signed" in this fashion.
I am wondering how to implement this. I understand how to check for their access privlages. how do I go about changing them however. eg The person can create Purchase orders under their privledge level. Once a supervisor approves it, how do I turn that access off?
Does each field need a calculation that checks if approved, then locks the field? How do you lock it?
In filemaker help, find the article: Editing record access privileges
Read the entire article, paying close attention to the sub-section titled "Entering a formula for limiting access on a record-by-record basis"
Ah, I see it now. You need to choose limited in order to be able to define the calculation. Many Thanks.