Trying for a specific gender?

Lol... I find this kind of funny to think you may have control over this... Our 5 yr old is a girl and our 3 year old is a boy... TTC #3 and my daughter keeps saying she wants a sister... so I have read a little bit about this... and basically it is believed that the Y sperm swim fast, but die quickly... whereas the X sperm swim slower and may live longer. So, the tips are to begin trying for baby girl immediately after your period ends and stop trying before your fertile peak. Lol... well we have BD for the past 3 days and my period just ended... I'm not going to stop though during my ovulation days... maybe a baby will be made this month *fingers crossed * gender doesn't matter... we won't be finding out anyway until birth... just find the subject fun and was wondering if anyone has tried this...? :)