Error Dialogue box pops up too many times

I have a script with a simple check to see if there are too many consecutive Nan's. It uses a cubic spline interpolation to fix NaN's but I don't want it to interpolate if there more then 20 consecutive Nan's in the program. I have an error dialogue box that comes up in a loop, but if there is more than one spot with more than 20 consecutive NaN's the error box comes up multiple times. i only want the dialogue box to open once if there is 1 or more places with 20 consecutive NaN's. Here is what I did, is there a better solution to creating the error box?

if true
  % code
check = flow;
check(~isnan(check))=0;
check(isnan(check))=1;
c=diff(check);
start=find(c==1)+1;
stop=find(c==-1)+1;
if length(stop)<length(start)
  stop=[stop start(end)+1];
end
if length(start)<length(stop)
  start=[start(1)-1 start];
end
out=stop-start;
for ii=1:length(out)
check(start(ii):(stop(ii)-1))=out(ii);
end
for ii=1:length(check)
  if check(ii)>20 
      errordlg('too many consecutive missing points to interpolate check your data set', 'User Malfunction')
  end
end

Answer 1

[Walter Roberson]

After the errordlg() call, still inside the "if", add the command

break;