tier 4 dependent to tier 4 student

I am a tier 4 dependent, my husband is the main student in a private highly trusted status college .Both of us came here together.our visa expires january 2012.After which he will join his job ,in the sea.He is a Mariner.
can i pursue a course and switch to tier 4 category before my visa expires, and my husband become my dependent while i am here in UK.
which colleges will i have to join to get a tier 4 visa for myself and a dependent visa for my husband.[/b]

You can do any course you like under your current status for as long as that is valid but you can´t actually switch your status into Tier 4 from inside the UK. Nor can your partner switch his status from Tier 4 to PBS dependant from inside the UK.

if i go back to my home country,and apply from there.
is it possible then?

It's required that you apply from your home country.

if i apply from my home country now,is it possible that my husband be my dependent, before his tier 4 visa expires.

If you visa is granted, your husband can apply as your dependant (also from outside the UK). Or, better, you can apply together.