Hi.
i don't know if you set it up this way but i would use a float add and set per second.
and add for example -1 per second.
and a float clamp (set to 0 and set to a max speed)
on the same state have Set velocity and also a float compare to check if 0 or
on button fsm use 'Fsm Float Add' ([urlhttps://hutonggames.fogbugz.com/default.asp?W1181]Ecosystem[/url])on each click
The add value you could also manipulate from another fsm so that it would gradually deduct faster if a longer period no button was pressed