"Currently I'm doing this one-by-one..."
How are you doing this?
You talk of "Cells D19:D234568"; is the data in a spreadsheet or are you just using the nomenclature to describe the issue?
"_There must be a simple way of doing this quickly, no?"_
Depends on whether the data are in a simple text file or other form. There isn't any particularly efficient way to read a sequential text file by anything other than well, sequentially, no. IF (the proverbial "big if") it were fixed-length and fixed-width columns there are some tricks one can play in reading the file image as character array and selecting subsets, but if it is csv and the fields are variable width, then that doesn't work, either.
You could, of course, process line-by-line using several techniques, probably the best solution would be to use textscan and process the file in sizable "chunks" in a loop, selecting the columns of choice in each block.
If it were a spreadsheet, then xlsread can select ranges; I forget whether it can do disjoint ranges in a single call; it could be done with COM/ActiveX if not.
