Strange windows forms control bug?

[venomation]

I have the following code inside a Derived "Panel" control in C# 4:

    public void ForceMoveScrollBar(int distX, int distY)
    {

        if (Math.Abs(distX) > HorizontalScroll.Maximum - HorizontalScroll.Value)
        {
            HorizontalScroll.Value = HorizontalScroll.Maximum;
        }
        else
        {
            HorizontalScroll.Value += distX;
        }
    }

It is meant to scroll the horizontal scroll inside the panel by a certain amont when a key is clicked on the keyboard. However I have to tap the key twice for it to work, the first time make my panel flicker and the second time works. The only fix I have is:

public void ForceMoveScrollBar(int distX, int distY)
{

        if(Math.Abs(distX) >HorizontalScroll.Maximum - HorizontalScroll.Value) 
        {
            HorizontalScroll.Value = HorizontalScroll.Maximum;
        }
        else
        {
            //The value does not set on the first assigment!
            HorizontalScroll.Value += distX;
            //so I add another one!?
            HorizontalScroll.Value += distX;
        }
    }

Why does it do this strange behaviour?

[simplefolk]

I'm assuming your using autoscroll I have had better luck setting the postion

int distX += HorizontalScroll.Value;
int distY += VerticalScroll.Value;
//do some sort of range check
//then set the AutoScrollPostion
AutoScrollPosition = new Point(x, y);

hope this helps