How Can I use VC++ dll with VB???

I can not refer this function in dll..... Help me~~

VC++ DLL does change the string and return.

ex) int chgmsg(char *a, char *b)

a is input string and b is output string...

some try was failed. only returned runtime error '49'...

I can not use this function in VB6...

p.s. : I'm sorry~ my english is bad~~ but i can read~~ somebody help me!