[VB6] disposed animated gif files

[Cambalinho]

i have 1 module for read diposed animated gif files.
but i belive that i have some errors on it
heres the code for read the disposed value:

DisposalCode(TotalFrames) = ((Asc(Mid$(sBuff, lngFind + 4, 1)) \ 4) And 3)

i belive that isn't right by some reason
0 - normal animation;
1 - frame1 + frame2(these frame has the same size)(transparent);
2 - frame1 + frame2(only part of the image for be changed)(transparent).
(at least i belive that these is the right "formulas")
can anyone help me?
thanks