add attribute group and create new attribute to this group

//for example:

// I will add a attribute group named 'Vendor' to 'Default' attribute set

function addAttributeGroup($group_name, $attrSetName,$sort_order) {
	$modelGroup = Mage::getModel('eav/entity_attribute_group');
	$attributeSetId = Mage::getModel('eav/entity_attribute_set')
	->load($attrSetName, 'attribute_set_name')
	->getAttributeSetId();
	$modelGroup->setAttributeGroupName($group_name) //change group name
	//link to the current set
	->setAttributeSetId($attributeSetId)
	//set the order in the set
	->setSortOrder($sort_order);
	//save the new group
	$modelGroup->save();
}

addAttributeGroup('Vendor', 'Default',100);

 //Then Create a Select drop down attribute and add it to the group

function createSelectAttribute($code, $label, $group_name )
{
	$_attribute_data = array(
			'type'       => 'int',
			'input'      => 'select',
			'label'      => $label,
			'sort_order' => 1000,
			'required'   => false,
			'global'     => Mage_Catalog_Model_Resource_Eav_Attribute::SCOPE_STORE,
			'backend'    => 'eav/entity_attribute_backend_array',
			'option'     => array (
					'values' => array(
					)
			),
			'group' => $group_name,
			'visible' => true,
			'visible_on_front'=>true,
			'unique' => false,
			'is_configurable' => false,
			'used_for_promo_rules' => true,
	);
	
	$objCatalogEavSetup = Mage::getResourceModel('catalog/eav_mysql4_setup', 'core_setup');
	$attrIdTest = $objCatalogEavSetup->getAttributeId(Mage_Catalog_Model_Product::ENTITY, $code);
	if ($attrIdTest === false) {
		$objCatalogEavSetup->addAttribute(Mage_Catalog_Model_Product::ENTITY, $code, $_attribute_data);
	}
}

//add vendor name
createSelectAttribute('vendor_name','Vendor Name','Vendor');
//add vendor no
createSelectAttribute('vendor_no','Vendor Number','Vendor');

 //at Last i write a text format attribute function

function createTextAttribute($code, $label, $group_name )
{
	$_attribute_data = array(
			'type'       => 'varchar',
			'input'      => 'text',
			'label'      => $label,
			'required'   => false,
			'global'     => Mage_Catalog_Model_Resource_Eav_Attribute::SCOPE_STORE,
			'backend'    => '',
			'group' => $group_name,
			'visible' => true,
			'visible_on_front'=>true,
			'unique' => false,
			'is_configurable' => false,
			'used_for_promo_rules' => true
	);
	$objCatalogEavSetup = Mage::getResourceModel('catalog/eav_mysql4_setup', 'core_setup');
	$attrIdTest = $objCatalogEavSetup->getAttributeId(Mage_Catalog_Model_Product::ENTITY, $code);
	if ($attrIdTest === false) {
		$objCatalogEavSetup->addAttribute(Mage_Catalog_Model_Product::ENTITY, $code, $_attribute_data);
	}
}

//add vendor item no
createTextAttribute('vendor_item_no','Vendor Item Number','Vendor');