hi
since you posted in programming, perhaps a VB solution.....
Sub insertdash()
Dim r As Range, c As Range
Set r = Range("A2:A" & Cells(Rows.Count, "A").End(xlUp).Row)
For Each c In r
If Len(c) 5 Then
c.Value = Left(c, 2) & "-" & Right(c, Len(c) - 2)
Else
c.NumberFormat = "@" 'in case xl can interpret as a date
c.Value = Left(c, 1) & "-" & Right(c, Len(c) - 1)
End If
Next c
End Sub

regards
FSt1

"Striker3070" wrote:

I have a column of numbers, 5 digit up to 9 digit. I need to insert a dash
after the first number of any 5 digit number, and a dash after the second
digit if the number is longer than 5 digits.

so 12345 would need to become 1-2345
and 1234567 would need to become 12-34567

If my original numbers are in column A, I can make the new ones in Column B

.