If you want to creat X number of edit boxes use client side script like the answer posted here (2nd answer):

 

 http://stackoverflow.com/questions/5656392/how-to-create-input-type-text-dynamically

 

If you have an XPages input field with event handlers or converters etc. and you just want to make it appear on a button click. You can create it and set its "rendered"  propery to false and then use server side script to set it to true like below:

 

getComponent(controlID).setRendered(true);

 

 this will make it appear on the page when button is clicked