How to add multiple audio streams to AVI file using Video Edit SDK .Net

string video = @"x:\video1.avi";
string audio1 = @"x:\video1.avi";
int audio1TargetStream = 0;
string audio2 = @"x:\audio2.mp3";
int audio2TargetStream = 1;

VideoEdit1.Input_Clear_List();
VideoEdit1.Input_AddVideoFile(video, -1, -1, -1, VFVideoEditStretchMode.Letterbox, 1.0);
VideoEdit1.Input_AddAudioFile(audio1, -1, -1, -1, string.Empty, 0, audio1TargetStream0, tbSpeed.Value / 100.0);
VideoEdit1.Input_AddAudioFile(audio2, -1, -1, -1, string.Empty, 0, audio2TargetStream1, 1.0);