I suspected that might be the case, which is what I referred to in my last
sentence.
As a workbook is one file, the only way might be to copy everything from
workbook A to a sheet in workbook B. Unfortunately this would mean the
combned sheets would then be one file, unless you they copy it back after
editing. Not a reliable thing to do as there are too many chances of error.
One option might be to use the Insert object facility to link to the second
file. Insert>Object>Create from file possibly selecting Link to file. I've
no real experience of doing this, so you'd be as well trying the different
options out on COPIES of your files, before committing to the originals.
HTH