Thank you, I will look into your example it looks like what I want. I am trying to change a field in a case when the case loads or is viewed but I am having trouble with that. I have a trigger changing the field when the case is edited, and I had written something like this. Any advice is much appriciated if I am not doing this efficiently.

public class caseChange {

public static void makeChange(Case[] cs){

Set<Id> caseIds = new Set<Id>();

Set<Id> internalUserIds = new Set<Id>();

Map<Id,Datetime> commentCommunicationToCaseMap = new Map<Id,Datetime>();

Map<Id,Datetime> emailCommunicationToCaseMap = new Map<Id,Datetime>();

for(Case c : cs)

{caseIds.add(c.Id);}

for(User u : [Select Id,UserType from User where UserType='Standard'])

{internalUserIds.add(u.Id);}

for(CaseComment cc : [Select IsPublished, CreatedDate, CreatedById,ParentId,CreatedBy.Username From CaseComment

where CreatedById In :internalUserIds and

ParentId in : caseIds and

IsPublished=true and

CreatedBy.Username <> 'systemuser@mydomain.com'

ORDER BY CreatedDate limit 1])

{commentCommunicationToCaseMap.put(cc.ParentId,cc.CreatedDate);}

for(EmailMessage e : [select Incoming, CreatedDate, CreatedById,ParentId,CreatedBy.Username From EmailMessage

where Incoming=false and

ParentId In :caseIds and

CreatedById In :internalUserIds and

CreatedBy.Username <> 'systemuser@mydomain.com'

ORDER BY CreatedDate limit 1])

{emailCommunicationToCaseMap.put(e.ParentId,e.CreatedDate);}

for(Case c : cs){

if(c.First_Public_Response__c==null&&commentCommunicationToCaseMap.get(c.Id)<emailCommunicationToCaseMap.get(c.Id)) {c.First_Public_Response__c = commentCommunicationToCaseMap.get(c.Id);}

else if (c.First_Public_Response__c==null&&commentCommunicationToCaseMap.get(c.Id)>emailCommunicationToCaseMap.get(c.Id))

{c.First_Public_Response__c = emailCommunicationToCaseMap.get(c.Id);}

}

}

For trying to make the case field change on case view I  have overridden the case view in case buttons and links setup to a VF page. I've tried using the standard controller, Case with apex page extension and page action to a page reference and tried calling to something similar to above in the page reference.