Mathcad Object

Escribi este codigo para ejecutar Mathcad en Excel. El primer argumento es un string con el nombre del objeto:
el que se pone en el cuadro de nombres. Funciona bastante bien, pero me gustarian dos cosas:
1. Usar paramarray, pero fallo, no me queda bien.
2. Aparentemente llama tantas instancias del programa como objectos halla. Necesitaría que llame a mathcad una sola vez, pues aparenta ser muy lenta la funcion asi como esta.

Nota: IsVector e IsMatrix son pequenas funciones que devuelven un bool.
No las pongo porque no son mias, se las pedí prestadas a Volpi, de foxteam.

Option Base 1
Option Explicit

Public Function mcad(mcd As String, Optional a1 As Variant, _
Optional a2 As Variant, Optional a3 As Variant, Optional a4 As Variant, Optional a5 As Variant, _
Optional a6 As Variant, Optional a7 As Variant, Optional a8 As Variant, Optional a9 As Variant) _
As Variant

On Error GoTo ErrLbl

Dim ws As Worksheet
Dim MathcadObject As Variant, obj As OLEObject
Dim outRe As Variant, outIm As Variant
Dim inRe As Variant, inIm As Variant
Dim h As Long, k As Long
Dim i As Long, j As Long
Dim n As Long, m As Long
Dim inx As String
Dim A(1 To 9) As Variant

k = 0
If (Not IsMissing(a1)) Then
A(k + 1) = a1: k = k + 1
ElseIf (Not IsMissing(a2)) Then
A(k + 1) = a2: k = k + 1
ElseIf (Not IsMissing(a3)) Then
A(k + 1) = a3: k = k + 1
ElseIf (Not IsMissing(a4)) Then
A(k + 1) = a4: k = k + 1
ElseIf (Not IsMissing(a5)) Then
A(k + 1) = a5: k = k + 1
ElseIf (Not IsMissing(a6)) Then
A(k + 1) = a6: k = k + 1
ElseIf (Not IsMissing(a7)) Then
A(k + 1) = a7: k = k + 1
ElseIf (Not IsMissing(a8)) Then
A(k + 1) = a8: k = k + 1
ElseIf (Not IsMissing(a9)) Then
A(k + 1) = a9: k = k + 1
End If

'Activate the Mathcad object
For Each ws In Worksheets
For Each obj In ws.OLEObjects
If obj.name = mcd Then
obj.Activate
obj.AutoLoad = True
Set MathcadObject = obj.Object
End If
Next obj
Next ws

For k = 1 To k

' Setup arguments
inRe = A(k)
inIm = A(k)
If IsMatrix(inIm) Then
n = UBound(inIm, 1)
m = UBound(inIm, 2)
ReDim inIm(1 To n, 1 To m)
For i = 1 To n
For j = 1 To m
inIm(i, j) = 0
Next j
Next i
Else
If IsVector(inIm) Then
n = UBound(inIm)
ReDim inIm(1 To n)
For i = 1 To n
inIm(i) = 0
Next i
Else
inIm = 0
End If
End If

' Send to Mathcad in0, in1, etc
inx = "in" & CStr(k - 1)
Call MathcadObject.SetComplex(inx & CStr(k), inRe, inIm)

Next k

' Recalculate
Call MathcadObject.Recalculate

' Read results from out0 to Excel's outRe, outIm
Call MathcadObject.getComplex("out0", outRe, outIm)

' Send the last value again to actualize mcad image
Call MathcadObject.SetComplex(inx, inRe, inIm)

' Recalculate again
Call MathcadObject.Recalculate
Call MathcadObject.getComplex("out0", outRe, outIm)

' Set the answer: Not implemented yet complex answers
'If outIm = 0 Then
mcad = outRe
'Else
' mcad = CStr(outRe) & " + I " & CStr(outIm)
'End If

ErrLbl:

End Function