Why error in log with NBarsUpEvent in for loop

[Lonneman]

Hi, I am trying to check if there was an NBarsUp or -Down event during the last 7 bars. I tried this, but it doesn't work and I get an error message in the log: "Error on calling 'OnBarUpdate' method [...] You are accessing an index with a value that is invalid since its out of range.":

  protected override void OnBarUpdate()
        {
            if (CurrentBar < 45)
                return;            
            
            bool bNBarsUpEvent = false;
            bool bNBarsDownEvent = false;
            
            for (int i = 0; i <= 7; i++)
            {
                double valueUp = NBarsUp(nBarsPeriod, true, true, true)[i]; 
                double valueDown = NBarsDown(nBarsPeriod, true, true, true)[i]; 

                if (valueUp == 1)                
                {
                    bNBarsUpEvent = true;    
                    BackColor = Color.Green;                        
                }                
                
                if (valueDown == 1)                
                {
                    bNBarsDownEvent = true;    
                    BackColor = Color.Red;                        
                }            
            }            
        }

I don't understand why it's not working.