Can a subaru hill holder clutch be adjusted?

The hill holder is not a clutch, it just holds the brakes till the the clutch is let out. There is an adjustment on the cable, loosen the lock nut and tighten the second nut for more brake, loosen for less. Don't tighten too much at once, or you brakes will not release all the way. If your clutch is going out, there is no adjustment for that on a '99, its hydraulic and does not have a cable.