You need to define the behaviour you want when the user does not enter a valid file name, as in this case.
When you do not provide a file extension, xlsread will assume .xls . If you want to prevent that, and have it attempt to open the name with no extension, then add a '.' on to the end of the name, as in
xlsread([A '.'])
I would suggest you do input validation before you invoke xlsread to ensure that the name the user gave matches an actual file. You need to decide whether you want to force the user to give a full extension, and if not then you need to decide what order of extensions you want to try.
Might I suggest that this problem would be reduced if you were to use uigetfile() instead of input() to get the file names?
