contact form 7 dynamically add feilds if required

im using contact fomr 7 and its great but what if i wanted to have ahidden field that only appears if a user selects a checkbox?
basically depending on what they put in one field will decide if this other field appears or is hidden because its not relevant to them.

this requires javascript. does cf7 support this or msut i figure it out with jquery myself? if so any help towards the right direction would be great!
i know i can use $(‘field’).hide
but how would i say to unhide if a checkbox was checked?

$(‘checkbox’).change ?