The short answer is, in general, you can’t do this. Without knowing more details of your scenario, perhaps the best that can be offered up is to cut your column block to a new editor tab, perform your replace operation there (on that entire doc), rectangular-select the new contents, and copy and paste back into the original doc.

Of course, if you provide more detail, perhaps a regular-expression search-and-replace operation could be crafted to do what you need, or possibly the description would allow other solutions to be brought to light…