Sub Macro1()
' Right-click a cell
    Range("C10").Select
' From the context menu, click "Hyperlink...", and in there fill in the dialog
    ActiveSheet.Hyperlinks.Add Anchor:=Selection, Address:= _
        "http://blah.example.com", TextToDisplay:="foo"
    Range("C10").Select
' Right-click cell again, do "Edit Hyperlink..." and s/foo/bar/
    Selection.Hyperlinks(1).TextToDisplay = "bar"
End Sub