This is INCORRECT...

high BUTTON0=1

You've aliased BUTTON0 as a pin on your pic... now are you using it as an INPUT in which case you need an IF statement, or are you using it as an OUTPUT in which case you can use the HIGH statement...

Let's assume you're using it as an INPUT and checking is it has been pressed... Buttons are usually pulled LOW when pressed because they are connected between the PIC pin and 0v. There is usually a pull-up Resistor on the pin, but since you are using PORTB then you will find you can probably enable internal pull-up's to do that job... so in this case your statement would be...

If BUTTON0=0 then
HIGH LED
Pause 600
endif

Also, your DEFINE statements look awfully strange to me if you are using MeLabs PICBasic (which this forum is intended for)... if you are using anyone elses BASIC product, you might not get much help here...