Emilija,

It doesn't matter what functions you use, it is the total length of
the 'text' that counts. What could help
- Tools/Options/Calculation uncheck 'save external link values'
- Select the empty rows on the bottom of your sheet and delete them,
same goes for the columns (they may appear empty, but still contain
formatting info and the likes)
- Applying a formatting to an entire row or column often takes less
space then applying it to 100's of cells (Excel needs to remember only
once)
- Copying your sheets to a new workbook might also help because all
the internal clutter isn't copied with the sheets.

DQ