Fixed it... Thanks again for all your help Merjet!
-- Dan

Sub Clean_Data_File()
Dim iEnd As Long
Dim ws As Worksheet
Dim c As Range
Dim rng As Range
Dim iCt As Integer

Application.ScreenUpdating = False

Set ws = ActiveSheet
iEnd = ws.Cells(65536, 19).End(xlUp).Row
Set rng = ws.Range(ws.Cells(3, 19), Cells(iEnd, 19))
For Each c In rng
If InStr(c, "/") = False Then _
c = Mid(c, 4, 2) & "/" & Mid(c, 6, 2) _
& "/" & "20" & Mid(c, 2, 2)
Next c

iEnd = ws.Cells(65536, 20).End(xlUp).Row
Set rng = ws.Range(ws.Cells(3, 20), Cells(iEnd, 20))
For Each c In rng
If InStr(c, "/") = False Then _
c = Mid(c, 4, 2) & "/" & Mid(c, 6, 2) _
& "/" & "20" & Mid(c, 2, 2)
Next c

iEnd = ws.Cells(65536, 16).End(xlUp).Row
Set rng = ws.Range(ws.Cells(3, 16), Cells(iEnd, 16))
For Each c In rng
If InStr(c, "-") = False Then _
c = Mid(c, 5, 2) & "-" & Mid(c, 1, 3) _
& "-" & Mid(c, 8, 4)
Next c

Application.ScreenUpdating = True

End Sub