Re: Changing custom variables between pages?

So... this is what I am doing:

$url = 'http://'.$this->application->config->ANALYTICSURL.'/'.
'?module=API&method=CustomVariables.getCustomVariables&expanded=1'.
'&idSite=1'.
'&period=week&date=today'.
'&segment=visitorId=='.$customer_action_tracker->getVisitorId().
'&filter_sort_column=idvisit&filter_sort_order=desc&filter_limit=5'.
'&token_auth='.$this->application->config->ANALYTICSTOKEN.
'&format=PHP';

I get ALL the data for this visitor for the last week, including several different values I set for the custom variables.
&filter_sort_column=idvisit&filter_sort_order=desc - this doesn't seem to change anything, and filter_limit only limits the number of CustomVariables I get, not the number of rows I want to explore. In other words - how do I limit the call to only get the LAST row that was recorded for this visitor?