No question here, just a procedure example for the achive.

Find duplicate range or cell references (as precedents) in a cell's
formula - an example

Sub FormulaDuplicateRefCheck()
'Checks each cell's formula in the selection for any duplicate/
multiple reference
'to the same range in the formula

   Dim c, cell, evalCell, OriginalSelection As Range
   Dim acFormula, cAddress, FoundRange As String
   Dim CountCharacter, I As Integer
   '  On Error Resume Next
   Set OriginalSelection = Selection
   'Loop through each cell in the selection

   For Each evalCell In OriginalSelection
       On Error Resume Next

       'Turn the evaluated cell's formula into a string
       acFormula = evalCell.Formula
       'Turn the evaluated cell's precedent(s) address references
into into a string
       acPrecAddress =
evalCell.Precedents.Address(RowAbsolute:=False, ColumnAbsolute:=False)
       'Select the evaluated cell's precedent(s) address references

       evalCell.Precedents.Select

       ' Loop through each cell in the evaluated cell's precendents
cells
       For Each c In Selection
           'Turn each precedent cell address into a string
           cAddress = c.Address(RowAbsolute:=False,
ColumnAbsolute:=False)

           'compare the precedent cell address to the evaluated
cell's formula as a string
           'to indentify the number of occurrences of the precedent
cell's reference
           For I = 1 To Len(acFormula)
               If Mid(acFormula, I, Len(cAddress)) = cAddress Then
                   CountCharacter = CountCharacter + 1
               End If
           Next
           'if there is more than one occurence then add the
precedent cell address to
           'a string list
           If CountCharacter >= 2 Then
               FoundRange = FoundRange & vbLf & cAddress
           End If
           CountCharacter = 0

       Next c
       'Test for existence of items in the multiple reference string
list
       If Len(FoundRange) >= 1 Then

           MsgBox "Cell " & evalCell.Address(RowAbsolute:=False,
ColumnAbsolute:=False) _
                  & " has duplicate range reference(s): " &
FoundRange
       End If
       FoundRange = ""
   Next evalCell
   OriginalSelection.Select
End Sub

Note: the above code doesn't identify any duplicate Named Ranges. It
only works with standard cell range references.

Also:

Sub FormulaINCONSISTENCYCheck()
'Check a range of cells to see if their formulas are consistent
'when compared amongst themselves

'Consistent formulas in the region must reside to the left and
'right or above and below the cell containing the inconsistent
'formula for the InconsistentFormula property to work properly.

   Dim c As Range

   For Each c In Selection
       ' Perform check to see cell has an inconsistent formula
       If c.Errors.Item(xlInconsistentFormula).Value = True Then
           MsgBox "cell " & c.Address & " has an inconsistent
formula"
       End If
   Next c
End Sub

seach criteria:
precedent duplicate check
formula reference duplication
duplicate cell references check
duplicate precedents exist
range reference duplication
formula precedents audit
range or cell reference duplication error
formula inconsistent test