Using BlockInput(), You can not diasable the specific key becouse it will block the all input events of the system.
Look Here ->
http://msdn.microsoft.com/en-US/library/ms646290.aspx[
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If you want suspress specific key then handle the events of keyboard
and do the following inside the keyboard input handler
If keyascii = vbKeyF5 then
keyascii = 0
end if