passandola per riferimento così

codice:
Option Explicit

Private Sub Form_Load()
Dim a(100) As String
Dim i As Integer
For i = 0 To 100
    a(i) = i
Next
xxx a()

End Sub

Sub xxx(ByRef x() As String)
   Dim i As Integer
   For i = LBound(x) To UBound(x)
      Debug.Print x(i)
   Next
End Sub