How much can I adjust a partition's size on a Hard disk

That's what I thought—and in fact, I did that with two of the 4 partitions— I actually brought them down in size— (which worked perfectly)... so that would give me even more room to make a third section, larger than it was. But when I tried to make the third one larger: it wouldn't budge, even a single megabyte larger— even though I still have better than 200 GB to spare, on the entire (4-partitioned) drive! Is there a slot here that I can attach a screen shot? ...that shows a schematic of the (WD 1-terabyte) drive? I also just saw tonight, someone else's answer: that any given partition cannot be enlarged from the physical start-point of that sector (...not sure where that link was, but can eventually find it again!)... Have you ever come across that opinion before? Anyway: I tried dragging the RE-size control points from the bottom, OR the top: : but it just wouldn't budge !