I appologoze about the first post, looking at it now it wasn't descriptive enough.
So to be more specific...
Make a "block", then put two of them on the same "bar" (copy the "block", stretch the "bar" out longer, and paste the "block" at the end).
what you would get is somthing like this
[][]
where the -'s are just blank backgroung color
The key is to make the total area between the two "blocks" far enough they don't repeat and look weird, and also make the whole "bar" just slightly longer than the progressbar width.
for example:
Bootskin.ini
ProgressBarWidth = 195
bar.bmp = 236 wide
but this also depends on the size of the "blocks". What I like to do is move the last "block" a couple of pixels at a time so that the second "block" on the refresh lands exactly where the first one leaves the screen.
so this is what you get
-[1][2]-
1 is the starting point for that block and 2 is the end
so if you put a second block exactly at the 2 now it looks seamless
just try it you'll see.

hope I didn't bore ya or get too confusing