How do you link a Macro to a CommandButton.

Right now when I click on the button in design mode it references a
macro on the worksheet I am working on and it is trying to reference
another Macro. The macro is stored in a different file in another
directory. What is the file path to reference a Macro somewhere else?

So far my code in the commandbutton looks like this, but it doesn't do
anything when I click the button. I am missing some part of the path
to find the Macro. Can anyone help me?

Private Sub File_Updated_Click()

Public Sub Fileupdate()

End Sub

Thank you for your help!
Kristina