Shouldn't be anything stopping you from saving the worksheet as a .csv delimited by <whatever> and importing it into something else. It sounds like this could be a better way of doing the job than using Excel. I guess the question at hand is: What would you rather be doing this with/in, and is the only acceptable answer one that uses Excel?
Edit: In any case, it should be as simple as typing it out (e.g. =DEC2HEX(HEX2DEC(A1) + HEX2DEC(B1

), click dragging the + symbol by clicking on the bottom right of the cell and dragging it all the way down the worksheet. That'll automatically apply the formula to the entire worksheet as long as the values are organized row-by-row in separate columns. Like this:
1234
Sorry if I'm oversimplifying this. No sample set of data or anything, but even if it's more complicated than that, the premise should remain the same unless I'm missing something here...
Well, your first point hits on an added complexity I didn't mention. Ultimately, I have to output all this data as XML, and I can do that easily in Excel. The XML tools I have access too at the office are way too clunky for complex worksheets so, yeah, in that regard using Excel is pretty much the only option. I should also mention that the company where I'm working hates investing in new tools, so the chances of me being able to secure budget for New Tool X is slim to none.
Unfortunately, your proposed solution doesn't work because, yes, the data is more complicated than that. Some of the memory regions in a series of rows use the same offset, so making the formula sequential doesn't work for them (I have to go back and edit so that multiple rows refer to the same cell); and some of the columns for base memory addresses are in different worksheets. I could probably get around the second issue by restructuring the worksheets, but I'm loathe to do that since the engineers are already familiar with the existing format and, to be blunt, are likely to push back against using a totally new arrangement. I should also add that there is a logical reason to organize the data in the existing way, it just happens to make my particular task less efficient.
Radically simplified, the data looks like this:
Worksheet 1: Masters (Region Name, Start, End)
Region_1 00000000 0000FFFF
Region_2 0FFF1111 0FFFFFFF
Worksheet 2: Offsets (Name, Mask)
Region_1 C0000000
Region_2 A0000000
Worksheet 3: Results in XML (Name, Calculated Start, Calculated End)
Region_1 C0000000 C000FFFF
Region_2 AFFF1111 AFFFFFFF
Just note that in the real data Region_1 and Region_2 might be 27 or whatever rows apart, and there are 6+ masters that use the same offset but different base regions, and there are 4 types of start/end address for each row. Maybe the following capture will help...