Create a timer, and set it to an interval of one second.
Create a global integer variable count, and set it to minus one.
Set the count to 60 when you load the document.
In the OnTimer event method, check the count.
If it's negative, ignore it.
Otherwise, reduce it by one and check it again.
If it's zero, set it to 60, and save the document
This may help:
MFC - Timer - Tutorialspoint[
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