Changing Cell Colors With Vba

I'm trying to have change if the date on it is passed "now()". I am already using the 3 conditional formatting fields and need this one and another one. Here are 2 problems I seem to be having.

First - the code below only works if I change the date on the cell. I want code to either work with Worksheet Active or any other way so the user does not have to redo the date’s everyday.
Second - a record might have conditional formatting already. Is it possible for the target cell in this code can show this color while the rest of the row shows the color of the conditional formatting?

Private Sub Worksheet_Change(ByVal Target As Range)
Dim icolor As Integer
If Not Intersect(Target, Range("G1:G2000")) Is Nothing Then
Select Case Target
Case Is <= Now()
icolor = 39

End Select

Target.Interior.ColorIndex = icolor
End If

End Sub