New to using a canvas

Hello all, I am running a staircase procedure to find a blur threshold. People see a .bmp of a word for 67 ms and try to identify it. If they do, it gets blurrier, if they don't, it gets less blurry (more or less). I tried Generate PreRun to load all of the .bmps at the top of the program, but that doesn't work because the filenames for the slides are [Word]_[Blur], and [Blur] is unknown until the previous trial is finished. So, I started looking into drawing it to an offscreen canvas, but honestly, the description in the E-Basic help is not helpful to a newbie. Which of all the canvas features do I need to load an existing .bmp and show it in the center of the screen? I also have a prerelease of 67 ms, but the program seems to be wanting to load the next image before it knows if the current trial is correct or not, and so it can't find [Word}_?.bmp.

Any help would be most appreciated!