how to keep helpdlg displayed while user manipulates plot

Here is what I am trying to do: plot a line, suggest to user (helpdlg) they zoom the plot so they can find some info about a spike in the data, put another inputdlg for them to enter the data info needed to define a ROI (region of interest) where we want to replace the spike data with a spline estimate.

Result of zooming below, but I need to move my "helpdlg" back to where I can see it (after zooming plot) in order to press the "OK" button:

Problem is that if I make the helpdlg modal, the user cannot zoom the plot but if I do not make it modal it gets obscured by the plot while they zoom it. So, how can I keep the "helpdlg" visible so they can push its button after zooming the plot? Or is there a better way to do this?

Once the data is entered, I calculate a spline fit to the data in the ROI and show them the result -- they can accept the fit or redefine the ROI. I do this with a "questdlg" but this also has problems -- it obscures the result (see plots below). Now I can manually move the "questdlg" window each time to see what is under it (as shown in the second plot), but that seems clumsy.

Here is my code:

 fp = plot(fx,fy,'-o');    %plot the line
 %user reminder to zoom plot to find the spike center and edges
 hb = helpdlg('Zoom to find spike center, just hit "enter" if zooming not needed', 'Zoom plot');
 waitfor(hb);      %wait for user to close the help dialog
 %put up the input dialog asking for 3 data parameters
 loc = inputdlg({'Center Channel : ';'Points to Left : ';'Points to Right : '},'Define the fit region',1,defAns);
 xc = str2double(loc{1});  %center channel number
 xl = str2double(loc{2});  %points to left
 xr = str2double(loc{3});  %points to right
 p1 = xc-xl-1;      %calc last point to left of fix ROI
 p2 = xc+xr+1;      %calc first point to right of fix ROI
 tr = [(xc-20):p1 p2:(xc+20)];  %region of good points near spike for spline
 ts = xc-xl:xc+xr;    %region to replace by spline interpolation

 est = interp1(tr,fy(tr),ts,'spline');      % spline estimate
 tss = [p1:p2];            % x-data just for plotting the fit line
 yss = [new(p1) est new(p2)];        % y-data just for plotting the fit line
 %plot original and fixed data in the expanded ROI 
 plot(fx(xc-20:xc+20),fy(xc-20:xc+20),'bo-',tss,yss,'r-',ts,est,'rs');
 %put up dialog to ask user if they like the fix result
 rply = questdlg('Accept the fix?','Options','Yes','Retry','No','No');

The result after the "questdlg" showing the dialog window obscuring the interesting region of the plot

Result after manually moving the "questdlg" window. What is the best way to specify a location for the "questdlg" so it does not obscure the interesting region of the plot below?

Thanks for your time. I am just a beginner in interactive, or UI, graphics in Matlab. Trying to learn.