Question concerning Xlim and Zoom

Hi Guys, I'm working on a GUI which includes a figure. For this figure I added two textboxes for xmin and xmax and set the limits fix to these limits using XLim. I want that the zoom function will not zoom out of theses limits. But I found a problem using the zoom-function: when I first zoom in and then out again, the figure is leaving these limits. BUT: when I try to zoom out first nothing happens. After this first zoom-out I can zoom in and out without leaving the given limits. Does anybody know, why? Here's my Code:

if get(handles.xBorder,'Value')==1
xMin=evalin('base','xMin');
xMax=evalin('base','xMax');
axes(handles.xyPlot)
set(gca,'XLim',[xMin xMax])

elseif get(handles.xBorder,'Value')==0
set(gca,'XLim',[1 10])   
end

xBorder is a clickbox which turn the limits on/off. At the moment the program reads the limits out of the base workspace - I changed it for debugging. I will afterwards change it back.