image - how to add a new field to an array of structures in Matlab -

i have large array of structures fields a(1:10000).image, a(1:10000).size, ...

i need add new field, let's a.number. need see a.image in order assign new field value a.number (an integer value).

this pseudo-code of need:

for k=1:10000     imshow(a(k).image)     enter number keyboard assigned a(k).number     load next image end 

i guess gui/script best. code in fast way?

how input?

for k=1:10000     imshow(a(k).image)     a(k).number = input('enter value'); end