.
The following prevents using CTRL/BREAK :

Sub preventCtrlBreak()
On Error GoTo MyErrorHandler:
t = Timer
Application.EnableCancelKey = xlErrorHandler


'#######################################################
'delete these lines if you don't want to inform the user ... also line above t = Timer
MsgBox "Now you can't use ctrl + break"
Do While Timer - t < 5
Loop
'#######################################################




MyErrorHandler:
If Err.Number = 18 Then
    MsgBox "Stop hitting ctrl + break !!!" '<-- change this line to your message UserName
    Resume
Else
    'Do something to make your impatient user happy
End If
End Sub