Can't you just put xlsread() in a loop and check the value. Then break from the loop once the cell is not empty. I'd also put a check on time since you don't want to get into an infinite loop you can't get out of, like wiat for 100 seconds or so
startTime = tic;
elapsedTime = toc(startTime);
while elaspedTime < 100
[numbers, strings, raw] = xlsread(......
if ~isempty(some cell........
break; % Exit from the loop since they entered something.
end
elapsedTime = toc(startTime);
end
