We need a little more detail.
At what point do you want them evaluated for whether to hide them? Whenever the value in C10 changes to "closed"? Click a button? Open the file?
When is it necessary? Are you expecting to unhide them manually or do you want code to do it? If you want code to do it, what event tells you to unhide them?
This will check all your sheets and hide the ones with "closed" in C10. But we need to wrap it in something that triggers it according to your answer to my first question.
VBA Code:
Dim WS As Worksheet
For Each WS In Worksheets
If WS.Visible = xlSheetVisible And UCase(WS.Range("C10")) = "CLOSED" Then
WS.Visible = xlSheetHidden
End If
Next WS