I want to call a form of InfoPath from Event Receiver. How Could I set a field infopath a Values, from Event Receivers to sets a Values on infopath fields which could I Validate and show or hide a sending button of Infopath form. Please help.
I do not believe you can OOTB (without using 3d-party tools or hacking subverting sharepoint model and architecture) call Infopath form code.
Answering the 2nd question:
you should acquaint yourself with Web Part connections (as published to Sharepoint Infopath form templates are available and can be use as Infopath Web Parts in ASPX Web Part pages):
Update (in answer to comment):
So, what do you call by "Infopath form" and in which context? which type of Infopath form, where are its template published and Infopath XML data form (or Infopath Web Part in a Web Part page?) on its basis stored?
which is for sharepoint library.
And from your previous questions I understood that you were dealing with sharepoint list where, in case of Infopath form of type Sharepoint List Form the code internals are locked or depends on how you use it