Clueless: GUI graph datastream in realtime

Hi!
I am pretty new to programming with Matlab so please dont yell at me too loud for asking stupid questions;

I am writing on a programm that displays and, upon a pushbutton callback,  logs some pressure sensor data in real time. 
The sensor data are retrieved by sending the sensor a query and listening to the answer. I put this in a loop to continuously receive Data. I already managed to display the Data by simply updating a static Text of the GUI while in the loop. Now I want to make it sexy by displaying the Data in relation to time by a graph but after 3 days of trying i give up.

What i want is a 2d yx-Graph with x representing time and y representing the pressure value. Since i receive data continuously It would be nice to have sort of an animatet graph that displays the last t minutes. For this I thougt about showing "now" on the far right of the X-Axis and the according y-value, then with the next looprun, have both move one timestep to the left and display the new value and the new "now" -point where the old ones have been before.

Does anybody have a clue for me how to start or for what kind of plots to look?
How can I turn my datestr(now,....) into somethiong matlab accepts as a value for the x axis?
Does anyone know any similar projetcs? 

I would be very happy if someone had an idea.
thanks anyway for reading,
Cyber
P.S. This is the loop:

% --- Outputs from this function are returned to the command line.
function varargout = Controler_GUI_OutputFcn(hObject, eventdata, handles) 

        global Exitflag; % To exit the loop - flag is set by a push button of the GUI
        global Writeflag; % To start/stop logging - flag is set by a toggle button
        % Variables for the Logfile
        global Filename;
        global Filenamepath;
        startline=2;
        column='A';

while Exitflag==1;
         axes(handles.axes1); % set axix1 as current active axes.

           Depth=get(sensor, 'getdata'); % Just pseudocode here; receive newest pressure value

           set(handles.text2,'String',Depth); % DISPLAY OF DATA IN DISPLAY

           % DISPLAY DATA IN GRAPH
       plot(handles.axes1,now,Depth); %complete mess- doesnt work
           refresh;

           if Writeflag==1; % record data ?
              xlswrite(Filenamepath,Depth,Filename,strcat(num2str(startline),column));         
              startline=startline+1;
           end

           guidata(hObject, handles);
           pause(0.2);

end
varargout{1} = handles.output;