Excel Formula Function - Convert Imported Negative Numbers

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Mirror Negatives

Anyone that has worked with imported numbers in Excel will often be left with the problem of imported negative numbers that have the negative sign to the right of the number. These are referred to as mirror negatives. This means Excel will not see your numbers as negative numbers and to make matters worse, it won't even see them as valid numbers.

SAP is one such program that does this with negative numbers, e.g 200- instead of -200.

Let's say you have a great long list of numbers you have just imported and some of them are those so-called negative numbers (mirror negatives). Your job is to convert these to valid negatives that Excel will recognize. For the purpose of the exercise we will make the range A1:A100. In cell B1 enter this formula;

=SUBSTITUTE(IF(RIGHT(TRIM(A1))="-",RIGHT(TRIM(A1))&A1,A1),"-","",2)+0

Copy this down as many cells as needed and then copy them and select cell A1 and go to Edit>Paste Special-Values , directly over the top of the originals.

To give you an idea on how the formula works enter this part of it in any cell where A1 has the text 200-

=RIGHT(TRIM(A1),1)&A1

You will end up with; -200- The TRIM function simply ensure there are no space characters in the cell. As we end up with -200- we next need to remove the second occurrence of the negative sign. This is what; the SUBSTITUTE function is doing. We have told it to substitute the second occurrence of "-" with "" (empty text). Now, the result returned is actually text (as that is what the SUBSTITUTE function returns) so we simply use +0 and Excel will convert it to a valid number.

If doing this is a common task you should consider a macro to make the job easier. Below is one that will do the task at hand in no time. It has been optimized for speed.

Sub ConvertMirrorNegatives()
Dim rCell As Range
Dim rRange As Range
Dim lCount As Long
Dim lLoop As Long If Selection.Cells.Count = 1 Then
  MsgBox "Please select the range to convert", vbInformation
  Exit Sub
End If

 

On Error Resume Next
Set rRange = Selection.SpecialCells(xlCellTypeConstants, xlTextValues)

 

If rRange Is Nothing Then
   MsgBox "No mirror negatives found", vbInformation
   On Error GoTo 0
   Exit Sub
End If



lCount = WorksheetFunction.CountIf(Selection, "*-")
Set rCell = Selection.Cells(1, 1)

  For lLoop = 1 To lCount
        Set rCell = rRange.Find(What:="*-", After:=rCell, _
                    LookIn:=xlValues, LookAt:=xlPart, _
                    SearchOrder:=xlByRows, SearchDirection:= _
                    xlNext, MatchCase:=False)
                
        rCell.Replace What:="-", Replacement:=""
        rCell = rCell * -1
  Next lLoop
On Error GoTo 0
End Sub

To use this macro, go to Tools>Macro>Visual Basic Editor (Alt+F11) and then to Insert>Module and paste in the code above. Click the top right X to return to Excel and go to Tools>Macro>Macros select ConvertMirrorNegatives then click Options and assign a shortcut key.

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