Hi Garry:

You can try the code I had posted earlier:

i = 1
For Each cell In Range("my_range")
i = i + 1
'insert new sheet
Worksheets.Add(After:=Sheet1).Name = "sheet" & i
Columns("C:C").Value = Columns("D:D").Value
Next

While the code does not do anything, it just proves my piont that
there is a bug in Excel.

And here is another bug:

I'm developping an application where people can optimize data given a
slew of options.

Each execution requires that an existing sheet with data must be
duplicated in order performe calculations,

I discovered that using Sheets("test").Copy After:=Sheets("test") will
fail after running the execution after about 100 times (It depends how
much data is on Sheets("test").

It forces the user to close Excel. Once reopened, it works again until
the nex time.

So I have used the copy/paste method and it works fine.

Maybe they are solutions to those issues but I am not a programmer by
profession.