Copy Excel sheet into IE environment

Hi all,
When I am using IE to open some Excel file (use asp code
and auto run VBA in the excel file) I name this file
is "A", then open other excel file (use excel environment)
I name this file is "B". I try to copy (using move or
copy function in excel) a work sheet from "A" to "B", the
function cannot show "B" file for me to select, but on the
other hand I try to copy (using same method) a work sheet
from "B" to "A", the function is work and show file "A" in
the selection box, if anyone know the reason, please tell
me and hlep me to fixed this problem????

Thanks,
Ivan