Are you trying to do this?
vb Code:
  1. Private Sub Command1_Click()
  2.     Dim a(1 To 15) As String, i As Long
  3.     Dim b As String
  4.     For i = 1 To 15
  5.         a(i) = "test" & i
  6.     Next
  7.     b = join(a, "#")
  8.     MsgBox b
  9. End Sub