Thanks for your answer.

When I copy a formula within the same sheet I select it, then I use
"Copy" and then I use"Paste Special" where I can select "Formula"
in the same way as I can select "Value" to copy just value.
When I try to do the same copying a formula to another workbook
I get a different kind of window which contains things like Object,
Format, Bitmap etc.but no "Formula" to choose.

I have never used something like formulas which point to another
sheet or workbook. I simply want to copy formulas and use the sheets
separately.
However if it was the only way to solve my problem I could consider it,
but at the moment I don't know how to do it.

What happens if you just open the other workbook and edit|copy and
edit|pastespecial values (or formulas).

If your formulas still point to worksheets in the original workbook, you may be
able to copy from the formula bar and paste into the formula bar.

I have a sheet where some of the columns are calculated as a combination
of data in other columns. I use formulas to do it.
When I want to copy any formula within the sheet it is easy using Spacial Paste.
I have also other sheets in the same or in other files which are very similar
but I don't know how to copy my formulas there.