limbo - 5:28 pm on Jun 17, 2009 (gmt 0)

Why one exactly 3mb? Think I missed the point of that :) Surely if it's works to block a little over and permit little under you'll be fine?

As for file size—you could try creating a new document, then scaling the dimensions until you reach the desired file size (60cm x 21.75 cm @ 72 PPI was close on a quick test in PSCS3)-it displays it within the new file dialogue box. A bit crude but best I could think of.

Alternatively you resize the image in 3~5% increments (save, refresh file view, repeat) until you reach a few KB either side... Even cruder I suppose.