Welcome to the forum.
Doing stop-motion animation in PrE is easy, but as PrE is designed for common Video Frame Sizes, that 140 x 140 pixels will be tough. However, if you create your images at a larger size, that matches a common Video Frame Size, say 720 x 480, you can output to smaller size. In general terms, Video is horizontal rectangular.
To do the stop-motion animation in PrE, irrespective of that Frame Size, you would go to Edit>Preferences>General>Still Frame Duration, and there, you can set that Duration from 1 Frame, to almost infinity. Note: unlike some other settings on that General screne, the Still Frame Duration is in Frames.
You might be better off using a program like Photoshop Elements, and outputting to an Animated GIF. There are also many Animated GIF programs available, and many are free.
Adobe Flash would be a great choice, but it's not inexpensive. Same for Adobe After Effects. Both of those are designed to do all sorts of non-standard Video animations. However, for the price of either of those, one could buy dozens of Animated GIF creation programs.
PrE can do similar with Animated GIF (I could not find this in PrE 11, but others found it in previous versions), but due to its design around common Video specs., there will be limitations to overcome.
Thank you very much for your big help! I have made some wmv files with PrE in size 140 x 140 pixels, but the quality is not so good. I will try download Flash Professional CS6 trial version and make it in Gif. I hope the quality will get better.
Have a nice day.