I put the Round in the dll and it speeded things up a bit more again.
I don't need the Property Let as the max is available in the dll from the
ubound of the array.

RBS

Yes, I knew the Property Let MaxVal was redundant, it was only to show how
to put it there if required.

I was interested to see the "Event" driven method you had devised with
Chip's suggestion. From your original question it seems the main purpose of
all this is to update progress of a VB6 function on an Excel vba form. I've
been playing, seems it's possible to update the vba form directly from VB6 -

'in a VB6 Project named "vb2vba_Update"
'code in class named "clsTest"

Option Explicit

'Dim oVBAform As Object
'
'Public Property Set UsrFrm(oUF As Object)
'''/oVBAform = a Userform from VBA
'If Not oUF Is oVBAform Then
'Set oVBAform = oUF
'End If
'End Property

Public Sub Proc1(oVBAform As Object)
Dim i As Long
Dim nUpper As Long
Dim dPcent As Double
Dim nProgess As Long

nUpper = 12345678
dPcent = nUpper / 100

nProgess = 1

oVBAform.Caption = nProgess & "0%"

For i = 1 To nUpper
'do stuff
If i nProgess * dPcent Then
'Debug.Print i, nProgess, nProgess * dPcent
oVBAform.Caption = nProgess & "%"
nProgess = nProgess + 1
If nProgess Mod 10 = 0 Then
oVBAform.BackColor = 16777215 * Rnd
oVBAform.Repaint
End If
End If
Next

oVBAform.Caption = "Done"
oVBAform.CommandButton1.BackColor = 16777215 * Rnd
oVBAform.CommandButton1.Caption = "Close Me Now"

End Sub

'code in an Excel vba Userform
'with two commandbuttons

Option Explicit

Private Sub CommandButton1_Click()
Unload Me
End Sub

Private Sub CommandButton2_Click()
Dim oVB6 As New vb2vba_Update.clsTest

oVB6.proc1 Me
Set oVB6 = Nothing

End Sub

Private Sub UserForm_Activate()

Me.CommandButton1.Caption = "Quit"
Me.CommandButton2.Caption = "vb6 Proc1"

End Sub

In VB6, name the project and class as described above, run with F5 or
Ctrl-F5
Then, in Excel set a reference to "vb2vba_Update" which should appear in the
list, and run the form.

Normally, would probably want to declare and set object references in both
vb & vba at global level. To simplify in this example, I've kept all ref's
at procedure level. But I've left some commented stuff at top of clsTest,
which could be called from (say) the vba form initialize event.

I'm pretty new at this VBVBA stuff, so please nobody assume this is the
correct way of doing things, or that writing to the vba form direct from vb6
is better than the Event driven method. However it seems to work, somewhat
to my surprise!

Regards,
Peter T