AR Animation issue in Unity

I am trying a animation with AR using unity and Metaio sdk. I have to play that animation step by step when I try the below script it works perfect on ipad and android mobile device.

         Variable declaration
         ********************
               public GUIStyle buttonTextStyle;
               public Texture aTexture;
               private int curretnStep=1;
               GameObject gameObject;
               float SizeFactor;
               Texture2D texture;                  
               Animator CMTD42M ;
               bool isplaystarted = false;
               int[] videolengtharray = new int[6];
               int CurrentFrame=0;  
               bool islocked = false;

               *************
                  if (GUIUtilities.ButtonWithText (new Rect (Screen.width - 160,                            Screen.height - 100, 160, 100), "Next", null, buttonTextStyle)) {
            CMTD42M.speed=1;

            switch (curretnStep) {
            case 1:
                CMTD42M.Play ("First");
                break;
            case 2:
                CMTD42M.Play ("Second");
                break;
            case 3: 
                CMTD42M.Play ("Third");
                break;
            case 4:
                CMTD42M.Play ("Four");
                break;
            case 5:
                CMTD42M.Play ("Five");
                break;
            case 6:
                CMTD42M.Play ("Six");
                break;
            }
            curretnStep++;
            //isplaystarted = true;
        }

As I am running this script on Epson Moverio(Glasses) it dont take the button click event,so I used onMouseButtonDown As below script:-

    if (Input.GetMouseButtonDown (0)) {

            if ((new Rect (Screen.width - 160, Screen.height - 100, 160, 100)).Contains (Event.current.mousePosition))
            {

                CMTD42M.speed=1;

                switch (curretnStep) {
                case 1:
                    CMTD42M.Play ("First");
                    break;
                case 2:
                    CMTD42M.Play ("Second");
                    break;
                case 3: 
                    CMTD42M.Play ("Third");
                    break;
                case 4:
                    CMTD42M.Play ("Four");
                    break;
                case 5:
                    CMTD42M.Play ("Five");
                    break;
                case 6:
                    CMTD42M.Play ("Six");
                    break;
                }
                curretnStep++;
            }

        }

the animation is not playing step by step. it plays in different order..

Can ANybody help me, or please guide where I made mistake. I am new in Unity and AR developement

I get that Mouse-event proper. Is the problem in animation or in mouse click.. Please help..

Thanks bl0z0, I have written this code in OnGUI() function.

I finally solve my problem.. I am not getting the reason behind it.

The problem was in variable current step, when I do

         curretnStep++;

it was incremented by 2,not by 1.(only in Epson Moverio) so it was not taking proper switch-cases and animation plays wrong.