You can buy "aftertouch" pedals. They vary in cost, you can spend pretty much as little or as much as you'd like. You can set some velocity settings (volume) to control different parameters, for example sustain, filtering, etc - these are usually controlled via the VST instrument itself. On many the velocity can control multiple parameters at once, but it obviously then does change the actual mechanics of how you play which will be counter intuitive to your muscle memory. I'd never say using this budget way of doing things will equate to a fully realistic replication of an actual piano, but as something to play about with and enjoy it's a good compromise. You can even get fully weighted midi keyboards, and of course there's the option of a "proper" keyboard as it were - but they tend to be more expensive. As I say though, the distinct advantage is being able to actually mess about composing your own pieces - you can buy automated drumming VSTs that are pretty realistic, and basses etc - you'd be surprised nowadays what the tech can do! Anyway it's something you know is a potential option, give it some thought, maybe try and find a local music shop you can go and have a play with some in - and you're more than welcome, anytime.