There's no need for transparency here...
The only relevant thing is the position in which the images are loaded.
%V(X,X,X,X,-)
%x(X,<FILE_NAME>.bmp,X,X) <--- Background
%pb(X,X,X,X,<FILE_NAME>.bmp) <--- Progress bar
will work, but:
%V(X,X,X,X,-)
%pb(X,X,X,X,<FILE_NAME>.bmp) <--- Progress bar
%x(X,<FILE_NAME>.bmp,X,X) <--- Background
Will not.
This is because the draw order is respected, and we want the progressbar to be drawn over top of it's background.
[St.]