loop does not work

I have got a code which reads .xls file and plots the data, and I want to read and plot data continiously, but the loop is not working(((

function updateAxes (hObject, eventdata, handles)
xColNum = get(handles.popupmenuX, 'value');
yColNum = get(handles.popupmenuY, 'value');
fileName=handles.fileName;
while (1)
a= xlsread(fileName);
x=a(:,xColNum);
y=a(:,yColNum);
plot (handles.axes1,x,y);
pause (5)
end

[Jan]

"Is not working" is an insufficient description of the problem. Do you get an error message or do the results differ from your expectations? In the later case, describe both, please. It looks like you load and draw the same data repeatedly.