Where are you using the trigger expression; is it in a Multisample? Or do you have a Mix of Samples, each of which has its own Trigger expression? If each Sample has its own trigger expression, then
!KeyDown gateWhen: (!KeyNumber eq: 60)
should work. If you are using it in a Multisample, you'd want to both select a sample and trigger it. For example, if you had two samples, 'BD' (triggered by 60) and 'snare' (triggered by 61), then you could select the sample using the Index parameter field:
!KeyNumber - 60
and gate it using the Gate field
!KeyDown