Here is my solution...
using a to hold value next row of list, xx is the new value for the list. First check to see if it's in the list, if not add it, update a for next time, then go back to selection zz. Crude but it works
Code:
Sub Macro4()
a = Mid(Range("C1"), 2)
xx = ActiveCell.Value
zz = ActiveCell.Address
With Sheets("Automation Data").Range("B20:B100")
Set Rng = .Find(What:=xx, _
After:=.Cells(.Cells.Count), _
LookIn:=xlValues, _
LookAt:=xlWhole, _
SearchOrder:=xlByRows, _
SearchDirection:=xlNext, _
MatchCase:=False)
End With
If Not Rng Is Nothing Then
MsgBox "Already in List"
Exit Sub
Else
ttt = MsgBox("Not in List, Add now?", vbYesNo)
If ttt = 6 Then
Sheets("Automation Data").Range("B" & a) = xx
Range("C4:C5000").Select
With Selection.Validation
.Delete
.Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:=xlBetween, Formula1:="='Automation Data'!$B$20:$B$" & a
.IgnoreBlank = True
.InCellDropdown = True
.ShowInput = False
.ShowError = False
End With
Sheets("Customer").Range("C1") = "C" & a + 1
End If
End If
Range(zz).Select
End Sub