Help: "ByRef argument type mismatch"

[altf4]

Ok When I try to test my code here I get a

Compile error:
ByRef argument type mismatch


Here is the code:

Private Type ANSI_STRING
       Length           As Long
       MaximumLength    As Long
       Buffer           As Long
End Type

Private Type UNICODE_STRING
       Length           As Long
       MaximumLength    As Long
       Buffer           As Long
End Type

Private Declare Function RtlAnsiStringToUnicodeString Lib "ntdll.dll" (DestinationString As UNICODE_STRING, SourceString As ANSI_STRING, ByVal AllocateDestinationString As Boolean) As Long

'_____________________________________________________________

Private Sub Command1_Click()

    Dim UString     As UNICODE_STRING
    Dim AString     As ANSI_STRING
    Dim sKeyPath    As String
   
    sKeyPath = "\Registry\Machine\SOFTWARE"

    'Initialize ANSI_STRING:
    AString.Buffer = StrPtr(sKeyPath)
    AString.Length = LenB(sKeyPath)
    AString.MaximumLength = LenB(AString.Buffer)
    
    Dim pMem As Long: pMem = VarPtr(AString)    'get pointer of ANSI_STRING
    
    'Convert ANSI_STRING to UNICODE_STRING:
    'lStatus = RtlAnsiStringToUnicodeString(UString, ByVal VarPtr(AString), False)      'not work (ByRef Mismatch)
    lStatus = RtlAnsiStringToUnicodeString(UString, pMem, False)                        'not work (ByRef Mismatch)
    
    'Return Status:
        MsgBox GetSysMsg(lStatus)

End Sub

Note: GetSysMsg is a custom function in a module to return an status string based on any API's Return Value (Works for both STATUS and NTSTATUS)


Ok so here is the problem:
When ever I try to perform this, I get an error saying:

Compile error:
ByRef argument type mismatch

and it highlights pMem. Well I am a bit confused here to why it is saying this. So I attempted to pass it ByVal and it then says:

Compile error:
User-defined type may not be passed ByVal

so how am I supposed to pass this pointer to the API ??? I mean you would just think "Oh.. pass the structure not the pointer" in which it will execute then, but when it does, it will give a return status of "Invalid Pointer".

The API wants the pointer, I just need to know how to give it to it without VB giving an error.

Thanks for your help.



Here are the links to MSDN for the API and Structures:

RtlAnsiStringToUnicodeString Function:
http://msdn2.microsoft.com/en-us/library/ms648413.aspx

UNICODE_STRING:
http://msdn2.microsoft.com/en-us/library/aa491546.aspx

ANSI_STRING:
http://msdn2.microsoft.com/en-us/library/aa492030.aspx