Inserting Dashes between Letters and Numbers

Let's say you have a worksheet with lots of product codes in column A. These codes are in the format A4, B12, AD4, etc. Due to a change in the way your company operates, you are directed to change all the product codes so they contain a dash between the letters and the numbers.

There are several ways you can perform this task. If the structure of your product codes is consistent, then inserting the dashes is a snap. For instance, if there will always be a single letter followed by numbers, then you could use a formula such as this:

=LEFT(A1,1) & "-" & RIGHT(A1,LEN(A1)-1)

Chances are good that your data won't be structured, meaning you could have one or two letters followed by up to three digits. Thus, both A4 and QD284 would both be valid product codes. In this case, a solution formula takes a bit more creativity.

One way to handle it is with an array formula. Consider the following formula:

=REPLACE(A1,MATCH(FALSE,ISERROR(1*MID(A1,ROW(INDIRECT("1:100")),1)),0),0,"-")

If values are in A1-A10, you can put this formula into B1, and then copy it down the column. Since it is an array formula, it must be entered by pressing Ctrl+Shift+Enter. The formula finds the location of the first number in the cell and inserts a dash before it.

Assume, for the sake of example, that cell A1 contains BR27. The innermost part of the formula, INDIRECT("1:100"), converts the text 1:100 to a range. This is used so that inserting or deleting rows does not affect the formula. The next part of the formula, ROW(INDIRECT("1:100")), essentially creates an array of the values 1-100: 1,2,3,...,99,100. This is used to act on each character in the cell.

The next part, MID(A1,ROW(INDIRECT("1:100")),1), refers to each individual character in the string. This results in the array: "B", "R", "2", and "7". Multiplying the array by 1 (the next part of the formula) results in each of the individual characters being converted to a number. If the character is not a number, this conversion yields an error. In the case of the string being converted (BR27), this results in: #VALUE, #VALUE, 2, and 7.

The next step is to apply the ISERROR function to the results of the multiplication. This converts the errors to TRUE and the non-errors to FALSE, yielding TRUE, TRUE, FALSE, and FALSE. The MATCH function looks in the array of TRUE and FALSE values for an exact match of FALSE. In this example, the MATCH function returns the number 3, since the first FALSE value is in the third position of the array. At this point, we essentially know the location of the first number in the cell.

The final function is REPLACE, which is used to actually insert the dash into the source string, beginning at the third character.

As you can tell, the formula to perform the transformation can be a bit daunting to decipher. For those so inclined, it may be easier to just create a user-defined function. The following macro is an example of one that will return a string with the dash in the proper place:

Function DashIn(myText As String)
    Dim i As Integer
    Dim myCharCode As Integer
    Dim myLength As Integer

    Application.Volatile
    myLength = Len(myText)
    For i = 1 To myLength
        myCharCode = Asc(Mid(myText, i, 1))
        If myCharCode >= 48 And myCharCode <= 57 Then
            Exit For
        End If
    Next i
    If i = 1 Or i > myLength Then
        DashIn = myText
    Else
        DashIn = Left(myText, i - 1) & "-" _
          & Mid(myText, i, myLength - 1)
    End If
End Function

The macro examines each character in the original string, and when it finds the first numeric character, it inserts a dash at that point. You would use the function in this way:

=DashIn(A1)

ExcelTips is your source for cost-effective Microsoft Excel training. This tip (2613) applies to Microsoft Excel 97, 2000, 2002, and 2003. You can find a version of this tip for the ribbon interface of Excel (Excel 2007 and later) here: Inserting Dashes between Letters and Numbers.