DDE limitation?

[Julian Cox]

Hi all,

I've written a function (DDEsend, see below) to send some worksheet
cells to another application. DDEsend opens a DDE channel, loops
through the cells sending the value if valid and then closes the
channel. The function returns the number of items sent and only does
the DDEpoke if a commandbar button is down (on/off control). The
function works absolutely perfectly if it is called from another
command button or by running this function from the VB editor:

Function FakeIt()

Set QuickRange = ActiveSheet.Range("AB12:AB19011")
Sent = DDEsend(QuickRange)
Debug.Print Sent

End Function

The value printed is exactly what I expect and the data arrives at my
target app. All very nice.

However, if I call the function from a cell everything works except
the DDE. Here's what is in the cell:

=DDEsend(AB12:AB19011)

The value displayed in the cell is exactly what I expect and exactly
the same value as in the immediate window from FakeIt. But nothing
arrives by DDE. I want to call the function from a cell so that the
data is updated on change.

Here's the function:

Function DDEsend(SendRange)
Dim ChannelNumber As Long
Dim CellToPoke As Variant
Dim IDToPoke As Variant

' Setup handle to command bar button
Set ButtonHandle = CommandBars("Triguard").Controls(8)

' Only do DDE send if button is down
If ButtonHandle.State = msoButtonDown Then

' Setup DDE channel
ChannelNumber = Application.DDEInitiate( _
app:="WWserver", topic:="AUG_OUT")

' Counters
SentCells = 0
SkippedCells = 0

For Each Cell In SendRange
Set CellToPoke = Cell
If Not (Cell = "") Then
' Is it a discrete or a register
TypeToPoke = Cell.Offset(0, -17)

' Check the value is legal
Valid = CheckBounds(TypeToPoke, Cell)

If Valid Then
IDToPoke = Left(TypeToPoke, 1) & _
LTrim(Str(Cell.Offset(0, -18)))
' Send it
Application.DDEpoke _
ChannelNumber, IDToPoke, CellToPoke
SentCells = SentCells + 1
Else
SkippedCells = SkippedCells + 1
End If
End If
Next Cell

Application.DDETerminate ChannelNumber

If SkippedCells > 0 Then
PromptText = "Sent " & SentCells & " to WWServer. " & _
SkippedCells & " not sent due to invalid values."
Response = MsgBox(PromptText, vbOKOnly, _
"Wonderware stimulation")
End If

DDEsend = SentCells
Else
DDEsend = "Off"
End If

End Function

If I step through the code I can't see any differences in the data
types and values using the two call methods. What have I missed?
Have I hit a limitation of DDE, Excel or VBA?

Thanks in advance

Julian