>Thanks Cetin
>
>The function is COMPRESS. The interface (in VB) is the following:
>
>Declare Function compress Lib "ZLIB.DLL" (ByVal compr As
> String, comprLen As Any, ByVal buf As String, ByVal buflen
> As Long) As Integer

Oh you're following VB samples :)
Its original declaration is as :

int compress (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen);

Declaration in VFP :
Declare integer compress in "zlib.dll" ;
string @ dest, integer @ destLen, string @ src, integer srcLen

Cetin