I have a script here that  I found and is almost perfect for what I need.. although when pressing the button "add competition" i need it to create/ copy the record and add it to a different object "Test Competitors" which is a related list shown in page of  "Account" (related list).
Could anybody "tweak"/ adjust this script accordingly!? ]
("Test Competitors are competition of the accounts, not from the organization, they can be clients(accounts) while being competition of other clients(accounts)) 

What I believe is that the "add competition" button should trigger a creation of record in object "Test Competitors" unless this record already exist within the object, but also it needs to be added on the related list within accounts (if that makes sense)

If more information is required please let me know!! Thank you!


public class AccountSelectClassController{
 
    //Our collection of the class/wrapper objects wrapAccount
    public List<wrapAccount> wrapAccountList {get; set;}
    public List<Account> selectedAccounts{get;set;}
 
    public AccountSelectClassController(){
        if(wrapAccountList == null) {
            wrapAccountList = new List<wrapAccount>();
            for(Account a: [select Id, Name,BillingState, Website, Phone from Account limit 50]) {
                // As each Account is processed we create a new wrapAccount object and add it to the wrapAccountList
                wrapAccountList.add(new wrapAccount(a));
            }
        }
    }
 
    public void processSelected() {
    selectedAccounts = new List<Account>();
 
        for(wrapAccount wrapAccountObj : wrapAccountList) {
            if(wrapAccountObj.selected == true) {
                selectedAccounts.add(wrapAccountObj.acc);
            }
        }
    }



<apex:page controller="AccountSelectClassController" sidebar="false">
    <script type="text/javascript">
        function selectAllCheckboxes(obj,receivedInputID){
            var inputCheckBox = document.getElementsByTagName("input");
            for(var i=0; i<inputCheckBox.length; i++){
                if(inputCheckBox[i].id.indexOf(receivedInputID)!=-1){
                    inputCheckBox[i].checked = obj.checked;
                }
            }
        }
    </script>
    <apex:form >
        <apex:pageBlock >
            <apex:pageBlockButtons >
                <apex:commandButton value="Add to Competition" action="{!processSelected}" rerender="table2"/>
            </apex:pageBlockButtons>
 
            <apex:pageblockSection title="All Accounts" collapsible="false" columns="2">
 
                <apex:pageBlockTable value="{!wrapAccountList}" var="accWrap" id="table" title="All Accounts">
                    <apex:column >
                        <apex:facet name="header">
                            <apex:inputCheckbox onclick="selectAllCheckboxes(this,'inputId')"/>
                        </apex:facet>
                        <apex:inputCheckbox value="{!accWrap.selected}" id="inputId"/>
                    </apex:column>
                    <apex:column value="{!accWrap.acc.Name}" />
                    <apex:column value="{!accWrap.acc.BillingState}" />
                    <apex:column value="{!accWrap.acc.Phone}" />
                </apex:pageBlockTable>
 
                <apex:pageBlockTable value="{!selectedAccounts}" var="c" id="table2" title="Selected Accounts">
                    <apex:column value="{!c.Name}" headerValue="Account Name"/>
                    <apex:column value="{!c.BillingState}" headerValue="Billing State"/>
                    <apex:column value="{!c.Phone}" headerValue="Phone"/>
                </apex:pageBlockTable>
 
            </apex:pageblockSection>
        </apex:pageBlock>
    </apex:form>
 
</apex:page> 


Also I need this VF page to be popping up when clicking "new test competition" on the related list as picture below


If need anymore info please let me know.. I really appreciate the help!!

Thanks Vincent