You could use a small macro.
For example, this disables the F1 (help) key:
Option Explicit
Sub disableF1()
Application.OnKey "{f1}", ""
End Sub
And this would toggle it back to normal.
Sub enableF1()
Application.OnKey "{f1}"
End Sub
If you look at sendkeys in VBA's help, you'll see how to override special keys.
(Like ctrl-c for copy.)