protected override void Initialize()
    {
       // Make mouse visible
       this.IsMouseVisible = true;

   base.Initialize();
}

MouseState mouseStateCurrent, mouseStatePrevious;

protected override void Update(GameTime gameTime)
{
    // Allows the game to exit
    if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
    {
        this.Exit();
    }

    // Get current mouseState
    mouseStateCurrent = Mouse.GetState();

    // Left MouseClick
    if (mouseStateCurrent.LeftButton == ButtonState.Pressed)
    {
        // TODO when left mousebutton clicked
    }

    // Right MouseClick
    if (mouseStateCurrent.RightButton == ButtonState.Pressed && mouseStatePrevious.RightButton == ButtonState.Released)
    {
        //TODO when right mousebutton clicked
    }

    mouseStatePrevious = mouseStateCurrent;


    // Update
    base.Update(gameTime);
}

enum CLICKS{left=0, right, middle);
public void mouseClick(){
  mouseClick(-1);
}

public void mouseClick(int manualClick){

  if(mouseStateCurrent.LeftButton == ButtonState.Pressed || manualClick == CLICKS.left)
    leftClick();

}

public void leftClick(){
  //do stuff
}

public void randomFunction(){
  //doing stuff
  mouseClick(CLICKS.left); //<-- will simulate a left click
}