How can i always check if a cell is written in excel?

I want to know if there is a way (a loop or something) to check if it's written every cell in Excel (begging with A1), everytime I press a button in GUI and if it's not written, to write there. ( I already have a code to write in the next row but if i write in A1, A2, A3 and then erase what is written in A2, the next time I press the button it writes in A4, I want it to write in the empty cell A2)

Answer 1

[Alexandra Topciov]

I have solved the problem. I'm going to leave my example if anyone needs it:D

read Excel sheet

   [num,txt,raw]=xlsread('X.xls','X1');

copy data

     rowData={Z, X1, Y1, X2, X3, Y0, UP}; (the data i want to write)

make it go to next row

   row =(size(raw,1))+1;

search for empty row between data in and if it exists write in it then stop

    [nm, nn] = size(raw);
     for im=1:nm
         NaNIndex = find(isnan(raw{im}));
         if NaNIndex==1
             xlswrite(...);
            break
         end
     end

if there isn't an empty row write after the last row

if isempty(NaNIndex)
      xlswrite(...);
  end