Thanks, all, for the replies and ideas. I've looked at the available info on EQ7's "custom set" function, and its primary purpose seems to be to allow individual blocks to be set and sized anywhere on a quilt top. There is some block-drawing capability, but I don't trust that it will fully suit my needs.
Jennifer, how interesting that I'm not the only quilter using a spreadsheet program for quilt design! I actually created the design in Excel by making all cells the same size (approx. 1 inch square) and coloring/bordering multiple cells as needed. That was pretty straightforward, but figuring out how to print sections, when many individual pieces won't fit on a single printed page, is giving me a headache. I'm beginning to think getting my hands on some oversize graph paper might be my best bet.