Hi Dan,
Since they are dates, it seems one way would be to use
Conditional Formatting to check the date value in the column
to see if it is higher than a particular date.
http://www.mvps.org/dmcritchie/excel/condfmt.htm
Another way would be to use a Change Event macro
anything you change in Column A will have it's font, and it's interior
color changed. To reset change colors, double-click on cell A1.
Pasting from another cell will not cause the Change Event macro
to trigger, but manually entering a value will trigger the Change Event.
http://www.mvps.org/dmcritchie/excel/event.htm#chg010
Right click on the sheet tab, view code, insert the following code
Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
'reset change indications by double-clicking on cell A1
Cancel = True 'get out of edit mode
If Target.Address <> "$A$1" Then Exit Sub
Application.EnableEvents = False 'should be part of Change macro
Target.EntireColumn.Font.ColorIndex = xlColorIndexAutomatic
Target.EntireColumn.Interior.ColorIndex = xlNone
Application.EnableEvents = True 'should be part of Change macro
End Sub
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Column <> 1 Then Exit Sub 'only change if Column A
Application.EnableEvents = False 'should be part of Change macro
Target.Font.ColorIndex = 39
Target.Interior.ColorIndex = 19
Application.EnableEvents = True 'should be part of Change macro
End Sub
'For a different choice of color see
'
http://www.mvps.org/dmcritchie/excel/colors.htm
If your cell formatting includes a font color that font color will override
assigning a font color. So the cell background (interior color) not only
shows up better but may be necessary for a distinction, but I presented
a macro and you would customize it any way you want. In fact as a
worksheet event macro it would only affect the one worksheet, so
customization for the worksheet is centainly expected.
i.e. a typical number format negatives in Red 0.00_);[Red](0.00)
If you go with Conditional Formatting, then C.F. coloring overrides
other coloring options.
You can use Track Change, but I find the restrictions of shared workbooks
and the all or nothing approach very annoying, but you can read about that
(my opinions anyway) at
http://www.mvps.org/dmcritchie/excel/highlite.htm