I was worked lot of project for this layout based columncount on Magento Product listed page. But all time i was used only the XML solution. But that won’t work with multiple layout which is selected by admin on category layout section.
Now i can show the simple method to fix that problem on layout selection.
Go to the list.phtml file on your magento theme file.
There you can commend this line
$pageLayoutTemplate = $this->getLayout()->getBlock('root')->getTemplate(); switch ($pageLayoutTemplate) { case 'page/1column.phtml': $_columnCount = 5; break; case 'page/2columns-left.phtml': $_columnCount = 4; break; case 'page/2columns-right.phtml': $_columnCount = 4; break; case 'page/3columns.phtml': $_columnCount = 3; break; default: $_columnCount = 4; break; }