Based on an attribute of that row? No, at least not directly. Manipulating the width of a repeating section item requires modifying the properties of the .repitem element, which is the parent of the elements in the row. Instead of manipulting the repitem's width, however, you could make it an inline element (eg, display: inline-block), and manipulate the total width of its children. Something along these lines (untested): <fieldset class="repeating_example"> <input type="checkbox" name="attr_shrink" class="sheet-shrink"> <div class="sheet-repitem-body"> Lorem ipsum dolor sit amet </div> </fieldset> .repitem, .sheet-repitem-body { display: inline-block; } .sheet-repitem-body { width: calc(100% - 15px); } .sheet-shrink:checked + .sheet-repitem-body { width: calc(50% - 15px); }