"electro-hydraulic-EH- the valve actuator uses high pressure hydraulic liquid ( at 1500-3500 psig)to drive a piston than will move the valve actuator."
Does 3500psig work out to be about 238 bar? I'm used to seeing applications at 450bar (6000+psi).
If you want to vary your stroke length to follow desired pressures, you are best buying a pressure transducer (or a number of pressure switches?) to feedback to your control system. You could then use the signal to de-energise the control valve to neutral (assuming you have a neutral), stopping...