For how long i should take robitussin?

im going to take plain robitussin to improve the quality of my cm because i've read lots of encouraging things about it. im also on clomid and i read that i should start taking robitussin the day after i'll take my last pill. now i want to know for how many days should i take that syrup???? till my ovulation day??? should i BD every day around ovulation or every other day??? thanx in advance for the replies.