VBA Argument pass to DLL Issue

Hello,

So I'm completely new to VBA and I've written a DLL to do some functions and the idea is to pass the results back to Excel. The DLL works fine, I've tested it extensively. The issue is the last argument I pass to it from VBA in Excel, no matter what value it is, always gets passed as the same, very large number. Below is the VBA code and then the DLL function declaration. Help would be greatly appreciated I have no clue what's going on here. The last two arguments are to be passed as number values, both are passed in the same way, and the first works, the second doesn't.

VBA Code:

Option Explicit

' Declare the LMM Function that's in the DLL
Declare PtrSafe Function GenCudaLMMPaths Lib "C:\Path to DLL\LMMExcel.dll" Alias "GenerateCUDALMMPaths" (xTimes#, xRates#, xVols#, xRData#, ByVal ArrLen&, ByVal NPaths&) As Long


' Generate LMM Paths on Click
Sub LMM_Click()

    Dim Times#(), Rates#(), Vols#()
    
    Dim x As Long
    Dim y As Long
    Dim rTimes As Range
    Dim rRates As Range
    Dim rVols As Range
    Dim cell As Range
    
    Dim sz&
    sz = 15
    
    ' Resize
    ReDim Times(sz), Rates(sz), Vols(sz)
    
    ' Fill in Data
    Set rTimes = Sheets("Market").Range("C2:Q2")
    
    x = 1
    For Each cell In rTimes
        Times(x) = cell.Value
        x = x + 1
    Next
              
    Set rRates = Sheets("Market").Range("C5:Q5")
    
    x = 1
    For Each cell In rRates
        Rates(x) = cell.Value
        x = x + 1
    Next
        
    Set rVols = Sheets("Market").Range("C4:Q4")
    
    x = 1
    For Each cell In rVols
        Vols(x) = cell.Value / 10000
        x = x + 1
    Next
    
    'Call the Function
    Dim np&
    
    np = Sheets("LMM").Range("C2").Value
    
    Dim useCuda As Boolean
    
    If Sheets("LMM").Range("C3").Value = "GPU" Then
        useCuda = True
    Else
        useCuda = False
    End If
        
    Dim rData#()
    Dim rValue
        
    ReDim rData(np * sz * (sz + 3))
            
    rValue = GenCudaLMMPaths(Times(1), Rates(1), Vols(1), rData(1), sz, np)
    
    If rValue = -1 Then
        'No CUDA Card
        MsgBox ("Your system doesn't have a CUDA Enabled GPU")
    ElseIf rValue = 1 Then
        'Error Occurred
        MsgBox ("An error occurred while trying to generate LMM paths")
    ElseIf rValue = 0 Then
        'Success
        ' Need to reformat return data
        Dim fmtData()
    
        ReDim fmtData(np * sz, sz)

        Dim i, j, k
    
        For i = 0 To np - 1
            For j = 0 To np - 1
                For k = 0 To np - 1
                    fmtData(((i * sz) + j) + 1, k + 1) = rData(((i * sz * sz) + (j * sz) + k) + 1)
                Next k
            Next j
        Next i
    
        'Fill in data
        Sheets("LMM").Range("A8:K" & (np * sz)) = fmtData
    Else
        'Too many requested paths for this CUDA card
        MsgBox ("In order to prevent GPU Lock-up, you cannot request more than " & rValue & " paths.")
        Sheets("LMM").Range("C2").Value = rValue
    End If
    
End Sub

And here's the function definition from the .h file for the DLL:

int __stdcall GenerateCUDALMMPaths(double* arrTimes, double* arrRates, double* arrVols, double* retData, int ArrLen, int NPaths);

Thanks!

Yes, I can MsgBox(np) and it gives the correct value, but when I'm debugging and check the value once it's passed into the DLL it's completely different. What's weird is if I switch the ordering - pass in the np where the sz is and vice-versa, then the np is passed in fine but the sz is that same large number, which is really baffling.

Here's what's really weird. I tacked on another variable for the DLL function as a test/dummy variable. Then I pass np in both, in the first pass it gives the same large value - in the second the correct value. For some reason there's something off with the 6th argument, just that one.

Well the DLL isn't designed to be registered / doesn't have the proper register/unregister functions but I can try. In the meantime does anyone else have any ideas?