I have an excel workbook with multiple sheets. I want to save one of
the sheets as a WK4 in the background. I amusing the following code:

Sheets("sheetx").SaveAs Filename:= "C:\xxx.wk4", FileFormat:=xlWK4,
CreateBackup:=False

The problem is that although the excel appears to still be open with
all of the tabs, it has been renamed at the top to the WK4 filename.
If I close the excel and open the WK4 then it opens as WK4 with only
the sheet that I saved. My problem is that users may have an issue
with the excel being "lost" while the supposed WK4 file looks like
excel.

SaveCopyAs does not seem to help because that cannot be done against a
single sheet and cannot convert to WK4.

Any ideas about how I could do a SaveAs only in the background without
renaming the excel?