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:

/// <summary>
/// Lmcons.h
/// #define NET_API_STATUS DWORD
/// </summary>
public enum NET_API_STATUS : uint
{
    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
}

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