Rick,

Your code (in red) as it integrates with a snipet of my code. I am so greatful for this intricate and well devised code and the example it sets for the use of Evaluate, Intersect and xlWhole. I appreciate the opportunity to learn so much on a web site that has so many talented contributors.

Code:
Sub Freeze()
Dim Tt As Long
Dim Rb As Integer
Dim FirstRow As Long, LastRow As Long
Dim AddrA As String, AddrB As String
Dim RngA As Range, RngB As Range, RowRng As Range
Application.ScreenUpdating = False
On Error Resume Next
Sheets("INVESTOR INTERFACE").Activate
Application.Calculation = xlCalculationManual
With Sheets("INVESTOR INTERFACE")
    'FREEZE/STORE TICK-CITY DATABASE
    Let Tt = Application.Range("WHERE15").Value
    Let Rb = Application.Range("reachBACK").offset(0, -1).Value
    If Rb > Tt - 3 Then Rb = Tt - 4
        If Rb = 0 Then
        Exit Sub
        End If
    Set RngA = Sheets("INVESTOR INTERFACE").Range(.Cells(Tt, 128).offset(-Rb, 0), .Cells(Tt, 130))
    Set RngB = RngA.offset(0, 13)
    FirstRow = RngB(1).Row
    LastRow = RngA(1).offset(RngA.Rows.Count).Row - 1
    AddrA = Intersect(Rows(FirstRow & ":" & LastRow), Columns("DX:DZ")).Address
    AddrB = Intersect(Rows(FirstRow & ":" & LastRow), Columns("EK:EM")).Address
    Range(AddrB) = Evaluate("IF(" & AddrB & "=""""," & AddrA & ",IF(" & AddrA & _
                          "=""""," & AddrB & ",(" & AddrB & "+" & AddrA & ")/2))")
    Range(AddrB).Replace 0, "", xlWhole
    ' Erase formulas on this passing train so cells don't have to be calculated [35,000 rows]
    If Tt > 12 Then RngA.offset(-11, 0).Resize(24, 3).ClearContents
End With
On Error GoTo 0
Application.Calculation = xlCalculationAutomatic
End Sub
Steve