Provided by stand-alone DLLs that are intended to work with the Add-In Manager. This function provides information about a stand-alone DLL (XLL) for the benefit of the Add-In Manager.
LPXLOPER WINAPI xlAddInManagerInfo(LPXLOPER pxAction);
pxAction (xltypeInt or xltypeNum)
The information that is needed.
If pxAction is 1, returns a string (xltypeStr) containing the long name of the DLL.
If pxAction is any other value, returns a #VALUE! error.
\SAMPLES\FRAMEWRK\GENERIC.C
LPXLOPER WINAPI xlAddInManagerInfo(LPXLOPER xAction)
{
    static XLOPER xInfo, xIntAction;
    /*
    ** This code coerces the passed-in value to an integer.
    ** This is how the code determines what is being requested.
    ** If it receives a 1, it returns a string representing
    ** the long name. If it receives anything else, it
    ** returns a #VALUE! error.
    */
    Excel(xlCoerce, &xIntAction, 2, xAction, TempInt(xltypeInt));
    if(xIntAction.val.w == 1)     
    {
        xInfo.xltype = xltypeStr;
        xInfo.val.str = "\026Example Standalone DLL";
    }
    else
    {
        xInfo.xltype = xltypeErr;
        xInfo.val.err = xlerrValue;
    }
    return (LPXLOPER)&xInfo;
}