blockVal = get(hObject,'String');
% TLTL appears in 1st row, 1st column
% This should error check to make sure the string is between 0 and 9
% 1st expression tests if blockVal is all numbers, 2nd expression
% tests if blockVal is less than 0, 3rd expression tests if blockVal is
% greater than 9, 4th expression tests if blockVal is an integer
if (~(isstrprop(blockVal,'digit'))) || (str2num(blockVal) < 0) || ...
        (str2num(blockVal) > 9) || (isinteger(str2num(blockVal)))
    % Error about one digit numerics only
    errordlg('Block entries must be limited to the integers 0 to 9.  0 denotes any number possible.'...
        ,'One Digit Numeric Integers Only');
else
    puzzle(1,1).block = blockVal;
end