Another way to do it

Code:
ButtonPressCounter = 0

SWITCH-LOOP:
IF PORTx.x = 0 THEN     'this is where your button is connected to, obviously
   IF ButtonPressCounter = 3 THEN ButtonPressCounter = 0
   ButtonPressCounter    = ButtonPressCounter + 1
   IF ButtonPressCounter = 1 THEN GOSUB Program1:
   IF ButtonPressCounter = 2 THEN GOSUB Program2:
   IF ButtonPressCounter = 3 THEN GOSUB Program3:
ENDIF
GOTO SWITCH-LOOP:

Program1:
...do something
RETURN

Program2:
...do something
RETURN

Program3:
...do something
RETURN