How do I force FormatNumber to use a “-” to separate every “000”
Depending on my users culture on their computer
the result looks like “123 456 789.1235” or “123,456,789.1235”
How do I force it
Dim A As Decimal = "123456789.123456"
Dim B As String = FormatNumber(A, 4)
As @Andrew said, but if you want spaces (or dashes) you can just insert them in place of the commas.
Notice the trim statement. It removes any leading characters that may show up due to the length of a. I do like @Subs routine though, because it can handle a regardless of length. This one you have to put enough placeholders (#) in to deal with it.