The problem you're running in to is that PostcodeData is not an object. It's a structure. Luckily, the structure is composed of VFP compatible data types. You can create a long character string and pass that to the DLL.

ie.
cLookup = space(60)
cPostcode = space(8)
:
cReserved = space(50)

cPostcodeData = cLookup+cPostcode+...+cReserved

Once you have the string, pass the string by reference to the DLL function.

uretval = MyFunction(@cPostcodeData)

HTH.

>

Type PostcodeData
>  LOOKUP As String * 60
>  Postcode As String * 8
>  PostcodeType As String * 2
>  Organisation As String * 30
>  Property As String * 30
>  Street As String * 60
>  Locality As String * 60
>  Town As String * 30
>  County As String * 30
>  CountyOption As String * 1
>  MailSort As String * 5
>  STDCODE As String * 8
>  GridN As String * 6
>  GridE As String * 5
>  Reserved As String * 50
>End Type

>

DEFINE CLASS postcodedata AS CUSTOM
>	Lookup = ""
>	Postcode = ""
>	PostcodeType = ""
>	Organisation = ""
>	Property = ""
>	Street = ""
>	Locality = ""
>	Town = ""
>	County = ""
>	CountyOption = ""
>	Mailsort = ""
>	StdCode = ""
>	GridN = ""
>	GridE = ""
>	Reserved = ""
>ENDDEFINE