DateDiff returns the interval of time between two dates:
Sub DateDiffExample()
Debug.Print DateDiff("d", Now, "12/31/2010")
''Days until 12/31/2010
Debug.Print DateDiff("m", Now, "12/31/2010")
''Months until 12/31/2010
Debug.Print DateDiff("yyyy", Now, "12/31/2010")
''Years until 12/31/2010
Debug.Print DateDiff("q", Now, "12/31/2010")
''Quarters until 12/31/2010 End Sub