I'm using LibreOffice 3.6.4.3 on Ubuntu 12.10.

I use cell color and cell borders to group and distinguish groups of cells in my spreadsheet.

I have bold horizontal borders every 4 rows. This is a pain to do because you can't specify "embolden the borders on every nth row". So I do it manually, for enough of the spreadsheet as I need to deal with.

I'm developing the spreadsheet, so the I modify the formulae frequently. When I get the formula working for a cell, I propagate that formula to a bunch of rows below by dragging the cell's fill handle down to the other (several hundred) rows. The problem is that dragging the fill handle copies the cell formatting from the source cell(s) as well as the formula(e). This undoes the emboldened borders on every 4th row and re-colors all the cells too. I then have to select a group of 4 rows of cells and manually embolden the top and bottom borders for each group of 4 rows. It's very tedious.

Is there a way to drag the fill handle and propagate the formula(e) but not the cell formatting?