Below is a partial managed definition. The complete list of error codes is here:

http://msdn2.microsoft.com/en-us/library/aa370674.aspx

C# Definition:

    namespace Lmcons
    {
    /// <summary>
    /// Lmcons.h
    /// #define NET_API_STATUS DWORD
    /// </summary>
    public enum NET_API_STATUS : uint
    {
        NERR_Success = 0,
        /// <summary>
        /// This computer name is invalid.
        /// </summary>
        NERR_InvalidComputer = 2351,
        /// <summary>
        /// This operation is only allowed on the primary domain controller of the domain.
        /// </summary>
        NERR_NotPrimary = 2226,
        /// <summary>
        /// This operation is not allowed on this special group.
        /// </summary>
        NERR_SpeGroupOp = 2234,
        /// <summary>
        /// This operation is not allowed on the last administrative account.
        /// </summary>
        NERR_LastAdmin = 2452,
        /// <summary>
        /// The password parameter is invalid.
        /// </summary>
        NERR_BadPassword = 2203,
        /// <summary>
        /// The password does not meet the password policy requirements. Check the minimum password length, password complexity and password history requirements.
        /// </summary>
        NERR_PasswordTooShort = 2245,
        /// <summary>
        /// The user name could not be found.
        /// </summary>
        NERR_UserNotFound = 2221,

        ERROR_ACCESS_DENIED = 5,
        ERROR_NOT_ENOUGH_MEMORY = 8,
        ERROR_INVALID_PARAMETER = 87,
        ERROR_INVALID_NAME = 123,
        ERROR_INVALID_LEVEL = 124,
        ERROR_MORE_DATA = 234 ,
        ERROR_SESSION_CREDENTIAL_CONFLICT = 1219
    }
    }

VB Definition:

Public Enum NET_API_STATUS as UInteger
    NERR_Success = 0
    NERR_InvalidComputer = 2351
    NERR_NotPrimary = 2226
    NERR_SpeGroupOp = 2234
    NERR_LastAdmin = 2452
    NERR_BadPassword = 2203
    NERR_PasswordTooShort = 2245
    NERR_UserNotFound = 2221
    ERROR_ACCESS_DENIED = 5
    ERROR_NOT_ENOUGH_MEMORY = 8
    ERROR_INVALID_PARAMETER = 87
    ERROR_INVALID_NAME = 123
    ERROR_INVALID_LEVEL = 124
    ERROR_SESSION_CREDENTIAL_CONFLICT = 1219
End Enum