Increasing range of rf remote
 

Hello,
(Disclaimer - I am a novice electronics buff - just a few small
projects)
I have a small keychain remote used for advancing powerpoint slides.
It has an integrated laser pointer that is very useful in presenting
which is why I really want to get this to work.The remote is stated to
be 433 mhz. The reciever is a small box about the size of a pack of
cards.
Right now it has a range of about 40 feet (the product spec says 100')
I think it may have to do with the enviroment. We use it in a church
and there are several wierless mics ect.
I opened the recever and inside was a stiff wire antena bent into a
square about 1.5 inchs per side. It is soldered onto the board.
So I am wondering how I can increase the range of the
transmitter/recever. Can I just solder a longer antena? If possible I
would like it to be somewhat omni directinal. The product spec says it
is (is that why the square ant and not a long skinny one???)
Also while looking online I see places that sell 433 mhz ant's for
about 15$- They are made (I think) for handheld walki-talkies(??)
would somthing like this help me.

Any help would be much appreciated!
Thanx!
Keith