How frustrating

I'd suggest that it might be better / safer (in terms of the rules) to have Excel open. You can then copy and paste your calculations from Word into the formula bar in Excel, which will definitely calculate the answer for you. It's
slightly slower than using the calculate function, but you might find it quicker than using a traditional calculator? Using Excel as a replacement for your calculator in this way is fine under the current rules.
If anyone's still super keen to use the calculate function, then I'd suggest checking with the IFoA as they might say 'no' if it's not something available in all versions of Office. I'm afraid I don't know exactly where they're going to draw the line on these things!