Add navigation buttons to an AbstractCell

I've created an AbstractCell<String> to create the header that says "welcome to your mobile..." and I would like to add two buttons in this AbstractCell: the fist to return to the previous page, and the second to return to the welcome page.
I've used to create the header element a class that extends AbstractCell<String> using this code:

public class HeaderCell extends AbstractCell<String> {
 
     interface Templates extends SafeHtmlTemplates {
 
         String style = "HeaderPanel";
 
         @SafeHtmlTemplates.Template("<div class=\""+style+"\">{0}</div>")
         SafeHtml cell(SafeHtml value);
     }
 
     private Templates templates = GWT.create(Templates.class);
 
     interface templateWithButton extends SafeHtmlTemplates {
 
     }
     @Override
     public void render(com.google.gwt.cell.client.Cell.Context context,
             String value, SafeHtmlBuilder sb) {
         SafeHtml safeValue = SafeHtmlUtils.fromString(value);
 
         SafeHtml rendered = templates.cell(safeValue);
 
         sb.append(rendered);
     }
 
 }
 

Is there any way to add to add these two buttons?
Please notice the header cell wich is colored in black.
PS: To set the header element looking like the image below, I use this CSS:

.HeaderPanel {
     -moz-box-shadow: inset -1px -1px 15px 1px #ffffff;
     -webkit-box-shadow: inset -1px -1px 15px 1px #ffffff;
     box-shadow: inset -1px -1px 15px 1px #ffffff;
     background: -webkit-gradient(linear, left top, left bottom, color-stop(0.05, #242524
         ), color-stop(1, #242524) );
     background: -moz-linear-gradient(center top, #242524 5%, #242524 100%);
     background-color: #242524;
     -moz-border-radius: 7px;
     -webkit-border-radius: 7px;
     border-radius: 7px;
     border: 1px solid #dcdcdc;
     color: #ffffff;
     font-family: arial;
     font-size: 17px;
     font-weight: bold;
     padding: 8px 36px;
     text-decoration: none;
     text-shadow: 1px 1px 29px #ffffff;
     text-align: center;
 }
 

---