Concatenate selected columns

One way could be this.

You could use the following VBA function which joins (concatenates) the values from an arbitrary range of cells, with an optional delimiter.

Public Function Join(source As Range, Optional delimiter As String)
    Dim text As String
    Dim cell As Range: For Each cell In source.Cells
        If cell.Value = "" Then GoTo nextCell

        text = text & cell.Value & delimiter

nextCell:
    Next cell

    If text <> "" And delimiter <> "" Then
        text = Mid(text, 1, Len(text) - Len(delimiter))
    End If

    Join = text
End Function

For an example of how to use the function, enter =JOIN(A1:D1) into a cell anywhere on the spreadsheet.

I've done this with userform and there is a limit of 5 columns to be handled. My latest "creation" is now attached for enhancing.