How to Access two Screen by one button

How to Access two Screen by click one button but have processes One by One or step by step. screen 2 at first and if success (Register) can go to screen 3. is there a block that can join two of open another screen?

You will need to go to Screen2 first, complete the actions there, then from Screen2 go to Screen3, ensuring that you are switching screens correctly

Use different screens wisely

If you decided to use different screens, then you should switch them correctly, else you will run out of memory after a while...      
The recommended method of switching screens in App Inventor
(Thanks Taifun)
Also see demo: multiscreen.aia

thanks for your respon. but i mean how to put two control open onother screen in one command ("When IntrotoEntre Click")

Not possible. You can open Screen 2; do whatever you need to do on Screen2 and if successful, then go to Screen3. Before you do this, please read Tim's advice. You might be able to something similar to what you want using virtual screens but not with Screens.

Check the new extension added by Horacio Spinelli that allows you to issue different commands by multitaping a single button a different number of times. I think you could set up switching to different screens definitely ending on the number of taps on a single button