Modifying one value in all slots - Pattr

So if I have 3 slots in pattr each with 3 items for example:

SLOT1) a = 1; b = 2; c = 3;
SLOT2) a = 2; b = 4; c = 1;
SLOT3) a = 1; b = 3; c = 1;

Is there anyway I can overwrite all the values of c but leave the rest of the presets intact so that it becomes:

SLOT1) a = 1; b = 2; c = 0;
SLOT2) a = 2; b = 4; c = 0;
SLOT3) a = 1; b = 3; c = 0;

The only way I can think to do this is to load each in succession and replace individually but when there are a lot of slots this doesn't work too well.

Thanks.