Running Stored Procedure Within A Stored Procedure

I have a custom built users table for storing some values and I am also utilizing the aspnet_Users table. I want to delete a user from my users tables then execute the aspnet_Users_DeleteUser sproc and pass into the stored procedure the username of the user to delete because the DeleteUser method requires this. When I execute the command from within my asp.net web application I get the exception below. Both values are being obtained from the asp.net application and are represented in my DAL that is also below. Any thoughts as to why I am receiving this exception? Thanks.
Procedure or function 'aspnet_Users_DeleteUser' expects parameter '@UserName', which was not supplied.

 public static bool DeleteUser(int userID, string username)

{int result = 0;using (SqlConnection myConnection = new SqlConnection(AppConfiguration.ConnectionString))

{

SqlCommand myCommand = new SqlCommand("Users_DeleteUser", myConnection);myCommand.CommandType = CommandType.StoredProcedure;

myCommand.Parameters.AddWithValue("@UserID", userID);myCommand.Parameters.AddWithValue("@UserName", username);

try

{

myConnection.Open();

result = myCommand.ExecuteNonQuery();

myConnection.Close();

}catch (Exception ex)

{throw new Exception("There was a problem attempting to connect to the database to delete the record. {0}", ex);

}

}return result > 0;

}