Hello, again

I am at my end with this sink... but still can't afford a plumber!

It is the only drain in the house that has this problem.

I just tried using my hose and a small nozzel to put high pressure water through the drain in an attempt to unclog it... well here is the funny thing...

The sink will empty and the water will go straight from the hose down the drain... until I turn the water off... then about 3 inches of water comes back into the sink and won't drain... If I turn the hose back on, it will run for a few min and the sink will drain... then as soon as I turn it off, the water will stop draining... I have run the hose for extended periods and the water is going somewhere!! Its not coming up any other drains in the house... so what is the deal?

Any ideas will be appreciated! ;)

Your sink is connected to the drain line and it has what is called a re-vent, the sink vent is connected to the vent that is probably behind the commode.The water coming out of the hose is being forced up the re-vent and down the drain to the commode. As you stop the pressure the excess water then rises back the a level in your sink.
To stop this you have to run a small snake down the drain and hope it makes the right turns to go down the drain.