how to get value of uicontrol edit text without calling a function ?

I am trying to edit some data in real time by using a uicontrol edit box.

the box prompt me each value taken from an array (widths1), in a while loop (while i <= length(widths1)).

I would like to be able to rectify the value widths1(i) by typing in a number but somehow adding the function with the callback outside the while loop does not work.

I circumvented the problem in similar cases by adding a callback to a command in between ' ' (example 'edit = 1')

and adding an if cycle outside the uicontrol (example if edit==1, do something, end;)

however it does not seem to work in this case

            ea=uicontrol('style','Edit','string',widths1(i),'Position',[510 650 50 20],'callback','editA=1');
            eav=get(ea,'string')
            if editA==1
                widths1(i)=eav;
            end

I could also try

ea=uicontrol('style','Edit','string',widths1(i),'Position',[510 650 50 20],'callback','widths1(i)=XXX');

where XXX should be the updated 'string' value of the box... but somehow using get(ea,'value') inside the command does not work becasue "ea" is not recognized as object

I am stuck..