How Can I Train My Cat To Go To The Toilet Outside?

I disagree with Jim... Every cat I've had has started off using a litter tray because you have to keep the kitten indoors until they've had all their jabs etc.  However, as soon as they're allowed outside they much prefer to go there.  With previous cats the litter tray was just taken away as soon as they were able to go outside.   I now have a six year old cat who will hold it in until she goes outside, but I keep a litter tray in case I'm late home from work and can't let her out in time - she never uses it, not unless she's really really desperate.... I've recently got a new 3 year old cat and he uses it ALL the time, it's SO frustrating!!!  I don't want to get rid of it because I can be late home sometimes... I don't know what to do!  I've never had a cat that chooses to use a litter tray when they can go outside??!!    Any ideas?

I am having the same problem. I have two cats- aged 6 months. They will use the cat litter indoors but since ive been putting it outside they hold it in until bed time when I bring it back in for them. I didnt expect it to be so difficult to train them to use the toilet outside. The idea was to put their litter outside so they cry to go out, then start putting soil in the litter tray and then take it away all together.
Any other tips?

I'm having the exact same problem I have two cats a male who's three yeas old an a 8 month old female, my oldest cat was litter trained but now goes outside for the toilet but the youngest wont go outside ive tried moveing the litter tray slowly towards the door then leaving it outside the door but she comes in an then goes to the toilet in the bathroom :/ can anyone help me?