Respected Sir,

Thanks for your response, but I knew that the function has to be declared that way in VB.Actually I wanted to know how do I write that function in DLL by selecting Simple DLL option for Win32 DLL.

What I did was that I added a function after the DllMain function with the following declaration:
extern "C" __declspec(dllexport) double squareIt(double d)
{
return (d*d);
}

After doing so I complied the Dll,and everything was fine.
Then I added the compiled Dll into the system folder and the did the same as you have told me but I get the errors something like
"No Entry Point for Dll Found" Or "Bad Dll function call".

Regards,
ASHWANI PATHAK.