how to chose right subsequent for her2(erbb2)gene ? - (Apr/02/2012 )

I NEED URGENT HELP
How to chose right sequences for her2(erbb2)gene to design primer ? i want to detect the level of over expression of gene ?

I choose accession number (NM_004448) for HER2 (ERBB2) this is variant 1Transcript Variant: This variant (1) represents the shorter
transcript but encodes the longer isoform (a) . And there is variant 2 where this variant (2) contains additional exons at
its 5' end and lacks an alternate 5' noncoding exon, compared to
variant 1. These differences result in translation initiation at an
in-frame, downstream AUG and an isoform ( with a shorter
N-terminus compared to isoform a
.
i do not know what is differents between them ???????????? plz help me

You need to find out which variant you are looking for, which one is significant for your aplication.
If you're not sure, design primers that detect both.