This is the Class1, which have sub alfa and a parameter an array of type long.
Code:
Sub alfa(b() As Long)
Debug.Print "ok"
b(0) = 100
End Sub
It is impossible to have an array of type long in variant and pass it by reference. Except we can use invoke from iDispatch interface.

just add a reference to OLEEXP

Code:
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" ( _
    lpvDest As Any, lpvSource As Any, ByVal cbCopy As Long)
Sub main()
Dim k(20) As Long
Dim z, c As New Class1, arg() As Variant, Clid As Long, dispid As Long
Dim Disp As oleexp.IDispatch, ret As Long, riid As oleexp.UUID, lngArgErr As Long
Dim varDISPID() As Long, VarRet As Long, params As oleexp.DISPPARAMS, Excep As oleexp.EXCEPINFO
ReDim varDISPID(0 To 0)
Set Disp = c
ret = Disp.GetIDsOfNames(riid, "alfa", 1&, Clid, varDISPID(0))
If ret <> 0 Then Exit Sub
dispid = varDISPID(0)
z = k()
' we can't do this: c.alfa z
ReDim arg(0)
VarByRef VarPtr(arg(0)), z
With params
.cArgs = 1
.rgPointerToVariantArray = VarPtr(arg(0))
End With
ret = Disp.Invoke(dispid, riid, 0, 1, params, VarRet, Excep, lngArgErr)
VarByRefCleanRef VarPtr(arg(0))
Debug.Print z(0) = 100
End Sub




Sub VarByRef(ByVal a As Long, ByRef b As Variant)
Dim t(0 To 3) As Long
   CopyMemory t(0), ByVal VarPtr(b), 16
   t(0) = t(0) Or &H4000
   t(2) = VarPtr(b) + 8
   CopyMemory ByVal a, t(0), 16
End Sub
Sub VarByRefCleanRef(ByRef a As Long)
Dim t(0 To 3) As Long
   CopyMemory t(0), ByVal VarPtr(a), 2
   t(0) = t(0) And &HFFFFBFFF
   CopyMemory ByVal a, t(0), 2
End Sub


I have to say that OLEEXP has two faults on IDISPATCH:
One is from GetIDsOfNames, the rgsznames have to be Long. Using it as String is easy for one String, but we can't pass more strings and take with one call all the DISPID (and that happen if we use named parameters, so the first string is the name of function and the following strings are the name of parameters).

The second one is the return value from invoke, the VarRet. The right one has VARIANT type. The OLEEXP has this value as long type. I have check it and using as variant we can get UDT (from ActiveX dll).