write from MATLAB in to exist excel file

I have a problem when i want to want to save a value from matlab GUI (User Defined) into MATLAB. when I write the bath for the excel file its great new file with same name !!

Date sheet : the exist excel file

B15: the cell that want to be saved in

here is the code that I use:

a= str2double(get(handles.edit1,'string'));  %user inter the value to be saved
xlswrite('G:\MATLAB Examples\Data sheet',a,'Sheet1','B15'); % the cell to be save in

any suggestions for this problem ?

[Geoff]

Do you have the same problem if you specify the full filename? ie put ".xls" on the end.

[Samer Husam]

this is work... thanks a lot Geoff