C# Definition:

public enum MessageFilterAction
{
    /// <summary>
    /// Resets the window message filter for hWnd to the default. Any message allowed globally
    /// or process-wide will get through, but any message not included in those two categories,
    /// and which comes from a lower privileged process, will be blocked.
    /// </summary>
    MSGFLT_RESET = 0,
    /// <summary>
    /// Allows the message through the filter. This enables the message to be received by hWnd,
    /// regardless of the source of the message, even it comes from a lower privileged process.
    /// </summary>
    MSGFLT_ALLOW,
    /// <summary>
    /// Blocks the message to be delivered to hWnd if it comes from a lower privileged process,
    /// unless the message is allowed process-wide by using the ChangeWindowMessageFilter function or globally
    /// </summary>
    MSGFLT_DISALLOW
}

VB Definition:

Enum MessageFilterAction
   TODO
End Enum

Notes:

This isn't an official enum name, these values were put together from #Defines in the header file