[pmwiki-users] How to use different 'EditForm' in different group?

[imoc]

I've found many hints to allow PmWiki use different 'EditForm' in different 
group. e.g.: Cookbook/EditFormSamples and PmWiki.SitePreferences.

But since I don't know nothing about php, the hints did not help me to finish
what I want. Here is my need:

1) Using different 'EditForm' in different group;
2) If there is no custom GroupEditForm found, use the default;

How to write the conditional statements for this purpose? Thank for any help.

imoc