I made an VBA (version 6) function (as part of excel 2000 version
9.0.6926 SP3 add-in). This functions calls an external function
(within a dll).
As the external function is quite complex I can't really go into
detail, and I hope that that is also not needed (also difficult to
debug this dll;-).

This is the function (and the declaration of the external one):

'###################################################################
Public Function HeliacalJDutSE2(JDNDaysUTStart, Age, SN, Lat,
Longitude, HeightEye, Temperature, Pressure, RH, VR, ObjectName,
TypeEvent, Optional AVkind)

Dim serr As String
Dim dret(20) As Double
serr = String(256, 0)
If IsMissing(AVkind) Then AVkind = "vr"
' for some reason Excel tries the function with a JDNDaysUTStart
undefined!
' that is why there is this if then statement
If JDNDaysUTStart = 0 Then
HeliacalJDutSE2 = "#VALUE!"
Exit Function
End If
'1
i = HeliacalJDutSEf(JDNDaysUTStart, Age, SN, Lat, Longitude,
HeightEye, Temperature, Pressure, RH, VR, ObjectName + String(1, 0),
TypeEvent, AVkind + String(1, 0), dret(0), serr)
'2
If i = 0 Then
'3
HeliacalJDutSE2 = dret(0)
'4
Else
'5
HeliacalJDutSE2 = "#NORISE!"
'6
End If
'7
End Function


Private Declare Function HeliacalJDutSEf Lib "swedll32.dll" _
Alias "_HeliacalJDut@96" ( _
ByVal JDNDaysUTStart As Double, _
ByVal Age As Double, _
ByVal SN As Long, _
ByVal Lat As Double, _
ByVal Longitude As Double, _
ByVal HeightEye As Double, _
ByVal Temperature As Double, _
ByVal Pressure As Double, _
ByVal RH As Double, _
ByVal VR As Double, _
ByVal ObjectName As String, _
ByVal TypeEvent As Long, _
ByVal AVkind As String, _
ByRef dret As Double, _
ByVal serr As String _
) As Long ' dret must be first of 20 array elements
' serr must be able to hold 256 bytes


If I put a VBA breakpoint at '1; I get no value after resuming the
program (somewhere an error?)
If I put a break point at '2 or '3; I get the correct value for after
resuming the program (dret(0) is also correct at the breakpoint). So I
know that a good result can be produced!
If I put a breakpoint at '4, '5, '6 or '7; the program never reaches
these lines (so it jumps out (?) of it, due to an error?)...
If I comment out the line under '1; the programs ends as expected.

Strange or not? Pehraps you have 'fresh' eye on this piece of code of
mine?

Do I make somewhere an obvious error in my own VBA code?
I find it strange a breakpoint can change the behavoir of the
functions, so I must do somethign wrong. It could be in the external
function, but I have no means of debugging that one...
Or does this breakpoiint behavoir point to some 'obvious' error in the
external function?