I keep getting the following error message:

Run-time error '1004' Unable to set the Locked Property of the Range Class

I want to unlock the cell if the checkbox is checked and when it is not I want to set the cell to a formula and lock it.

Please help

Private Sub Check_Box_Click()
Worksheets("Sheet1").Unprotect ("password")
If Check_Box = True Then
Worksheets("Sheet1").Range("BB9").Locked = False
ElseIf Check_Box = False Then
Range("BB9").Formula = SpigDia(BB5, BB6)
Worksheets("Check_Box").Range("BB9").Locked = True
End If
Worksheets("Check_Box").Protect ("password")
End Sub
Thank you