c++ dll returning string

[Muk108]

i have no idea how to return a string from my dll here is some code i have so far

main.cpp

char *__stdcall myfunction(char * variable)
{
	return variable;
}

main.def

EXPORTS
      myfunction

vb code

Private Declare Function myfunction  Lib "my.dll" (ByVal variable As String) As String
 -----
MsgBox myfunction("test")

whats wrong i get a message saying it cant read the memory and also one that says it cant write to the memory... thanks for the help.