i remember it can be done, however microsoft did not like it. that 's the way we used to call SDK functions to supplement features not provided by VB.
it was something a bit like that (example provided without any warranty, i don't have VB6 anymore to test it)
VB:
Type composed
Dim field1 As Long
Dim field2 as Integer
EndType
Declare Function test Lib "test.dll" ( ByRef param As composed ) Return Long
Sub call()
Dim c As composed
Dim result As Long
c.field1 = 42
c.field2 = 7
result = test( c )
EndSub
C:
typedef struct
{
int field1;
short field2;
} composed;
int test( composed *param );
this is straight out of my mind. it may not work as is, as i can't verify it...
there was some pitfalls: VB integer type is 16 bits, strings are unicode, arrays are accessed as a SAFEARRAY in C (difficult to use). strings and arrays are to be avoided as they are very heavy in VB. there was a keyword like AddressOf to get a pointer to almost anythin. a function parameter in a declare statement can be declared as type "Any" which is the equivalent of C's "void". a special syntax of the Declare statement that i don't remember allowed to specify the real function name in the DLL to take care of name decorations (typically, the function above would be named "_test@4"). there are many many more things to say about that... the best way to find out is to open the API Viewer, which allows you to import Windows SDK functions into VB, see how things are declared there and match it with the C declaration in the SDK.
if you encounter some problem, tell them, i may be able to tell you what's wrong...
