For various reasons, I would prefer to use vba as opposed to
conditional formatting for my worksheet. If a duplicate value (in
this case, lengthy text entries) exists, change the font color to
blue. I can successfully write the macro for it but again, I would
prefer that it fire automatically on the Worksheet Selection Change
and I just can't figure how to make that work.

"=COUNTIF($D$1:$D$1000,D1)1"

Any assistance greatly appreciated as always.