You will have to do it in software which modifies all notes played based on MIDI CC data recevied from the HiHad pedal position. I don't know if any software can or cannot do it.
In cubase, no problem, you can use the input transformer which can set the note depending on the CC04 level.
There's a simple exemple in the Cubase manual that shows how to get filter all note off messages when pressing a sustain pedal. It's quite the same here, just set the filter to transform (instead of filter) and "pitch " to add 1 (= + & semi tone).
I'm sure there's many small VST (made with synthedit) which can make the same job with another vst host.
Just curiosity, which VST would you use to get harp sound ?