Need some urgent brake help - 87 c/20

[Cervantes]

Hik
Have a stock c/20 crew cab long box, old gov't truck. REplacing the front brake pads (disc). As far as I know, they were working fine before, just needed new pads. So, I removed the calipre, pulled off the old pads, opened the brake fluid resevoir and removed 3/4 of the fluid...but when I go to squeeze the piston back so I can fit the whole thing back on with new pads, I can't budge it! I put a c-clamp over the inner pad and went to town, but I can't get the darn thing to move.

I can't afford to replace the whole calipre, but I need to drive this thing come monday. If anyone has an Idea on how I can get it to move, I'd really appreciate it.

Thanks,
C