Sorry - using construct 0.99.96 - last "unstable" build
-> Sprite: Set 'old_x' to Sprite.Value('x')
-> Sprite: Set 'x' to Sprite.X
-> Text: Set text to (Sprite.X-Sprite.Value('old_x'))/Timedelta
'old_x' and 'x' - prvate variables. Text - just text to display current Speed.