Actually that is the default. The motion to raise the special levy should specify the purpose, and the amount raised can only be used for that purpose. So ensure that the wording of the motion is accurate.
However, be cautious of being too specific, as the remedial works may spread to unexpected tasks, when the work commences. For example, raising a special levy “to replace and upgrade the balconies, including the balustrades, by installing a water-proofing membrane and re-tiling the balcony floor”, seems good. But when the owners ask to have the walls re-painted, that does not fall within the wording. And what if one of the owners asks to install new lighting on the new balcony? Also not covered. It also depends on the owners. If all are happy with the project then there are unlikely to be any one objecting if the funds are spread to related features (but not to un-related tasks!). But if some owners are skeptical about the project, then you should ensure the wording covers exactly what you may be spending the money for.
If the project does not cost the full amount raised in the special levy, then the money left over can be re-assigned to another task, by making, passing and documenting this in a motion at a general meeting.