

$html['WindowLeftContents'] = HtmlTemplate::t_buffer(TemplateFileWindow1,$html);

$html['WindowCenterContents'] = HtmlTemplate::t_buffer(TemplateFileWindow2,$html);

$html['WindowRightContents'] = HtmlTemplate::t_buffer(TemplateFileWindow3,$html);

HtmlTemplate::t_include(TemplateFileMain, $html);

htmltemplate.inc
これしかしらない。が他にいろいろともありそう。