If you really want a computer controllable voltage, consider a system with DACs and ADC, similar to LTs Application note an86.
Avoid trimmers if possible, and if really needed take into account there usually poor TK and stability - so the trimmer should only do fine adjustment of something like 1% or less. Typical one uses a fixed resistor divider and the pot in parallel with a large resistor of something like 100 times the resistance from the wiper to the divider.