Write an OnChanging event handler to conditionally disallow changes to the value of Position. Set the AllowChange parameter to false to prevent a change to the current value of Position. 

OnChanging occurs both when the user clicks the arrow buttons of the up-down control and when an attempt is made to change the value of Position programmatically. To determine which button the user clicked, use the OnChangingEx event or the OnClick event, both of which follow the OnChanging event. 

CanChange 

OnClick 

OnChangingEx 

Position