Updating JSF panelGroup

I have the following code:

<h:panelGroup layout="block" id="foo">

                            <p:outputLabel for="requirementURL" value="Requirement URL" />
                            <br></br>

                            <p:inputText id="requirementURL"
                                value="#{data.data.requirementURL}"></p:inputText>

                            <p:commandButton actionListener="#{logic.addURL}" value="Add" icon="ui-icon-check">

                            </p:commandButton>
                            <br></br>

                            <p:outputLabel for="requirementsUrl" value="Requirements URL" />

                            <br></br>
                            <p:selectOneListbox id="requirementsUrl"
                                value="#{data.data.selectedURL}">
                                <f:selectItems value="#{data.data.requirementsDocuments}" />
                                <p:ajax event="dblclick" listener="#{logic.onDoubleClick}" />
                            </p:selectOneListbox>                           
                            <br></br>

                            <p:commandButton actionListener="#{logic.remove}" value="Remove"
                                icon="ui-icon-check" />

                        </h:panelGroup>

The thing I want to achieve is that each time I click some of the buttons Add or Remove to update the panel group so that the newly added item for example appear, I have tried several cases but didnt got any result :/