ADOBE interactive forms-make fields read only

Hello Experts,

I am developing a interactive forms using Webdynpro. in my forms I have many input enabled fields along with four buttons ( create, change,extend and submit). When user clicks on change button, I need to disable some fields ( access = read only),similarly when 'CREATE' is pressed I need to disable different set of fields as 'READ ONLY'. Also I have to make some fields as 'required in' in case of creation mode.

1. Is possible to control the access of the fields from the Webdynpro?, if yes then how? otherwise how to do this.

2. Is it possible to Hide/enable/disable/ a i/p field of Adobe form from Webdynpro? if yes how?

below is my form:

I would appreciate an early reply.