C# Definition:

    public enum MessageFilterInfo : uint
    {
        None=0, AlreadyAllowed=1, AlreadyDisAllowed=2, AllowedHigher=3
    };

    public enum ChangeWindowMessageFilterExAction : uint
    {
        Reset = 0, Allow = 1, DisAllow = 2
    };

    [StructLayout(LayoutKind.Sequential)]
    public struct CHANGEFILTERSTRUCT
    {
        public uint size;
        public MessageFilterInfo info;
    }

VB Definition:

User-Defined Field Types:

Notes:

Sample Code:

        CHANGEFILTERSTRUCT filterStatus = new CHANGEFILTERSTRUCT();
        filterStatus.size= (uint) Marshal.SizeOf(filterStatus);
        filterStatus.info = 0;
        ChangeWindowMessageFilterEx(Handle,_message,ChangeWindowMessageFilterExAction.Allow, ref filterStatus);