I wasn't able to find out or figure out but the page here http://help.exacttarget.com/en/documentation/exacttarget/content/ampscript/ampscript_syntax_guide/data_extension_ampscript_functions/#LookupOrderedRows suggests that we can create an AND clause within lookupOrderedRows. (Be awesome to create filters like that on the fly!) I don't see any directions on how. What we wish to do is filter the results first by a matched GUID code and then by a datestamp.
Set @rows2 = LookupOrderedRows("Cars",4,"Horsepower Desc","MPG",Field(@cardata,"MPG"), StartDate > NOW())
Does this need the word AND within the script or something else to make sense of the formula?