MSP430 Interrupt

Hi! I am trying to control servo motor with interrupt but it doesnt work :\ what is my mistake?How can I fix it?

#include <msp430.h>

void main( void )
{
  WDTCTL    = (WDTPW | WDTHOLD);       // Stop watchdog timer

  BCSCTL1   = CALBC1_1MHZ;             // Set DCO range
  DCOCTL    = CALDCO_1MHZ;             // Set DCO step and modulation

  P1DIR     =  0x04;                   // Set P1.2 to output-direction
  P1REN     =  (0x08 | 0x10 | 0x20);   // Enable resistors at P1.3/4/5
  P1OUT     =  (0x08 | 0x10 | 0x20);   // Pull-up resistors at P1.3/4/5
  P1IE  	= (0x08 | 0x10 | 0x20);
  P1IES		= (0x08 | 0x10 | 0x20);
  P1IFG 	= (0x08 | 0x10 | 0x20);
  P1SEL     =  0x04;                   // Set selection register 1 for timer-function



  TA0CCTL1  = OUTMOD_7;                // Reset/set
  TA0CCR0   = 20000;                   // Period
  TA0CCR1   = 1500;                    // Duty-cycle
  TA0CTL    = (TASSEL_2 | MC_1);       // SMCLK, timer in up-mode
  _BIS_SR(GIE);

  while( 1 )                           // Endless-loop (main-program)
  {}

  }
#pragma vector=PORT1_VECTOR
__interrupt void P1_ISR(void)
{
    if( !(P1IFG & 0x08) )               // Button at P1.3 pressed (S2 on LaunchPad)
    {
      TA0CCR1 = 1500;                  // Servo in middle position (1.5ms)
    }
    else if( !(P1IFG & 0x10) )          // Button at P1.4 pressed
    {
      TA0CCR1 = 1000;                  // Servo in minimum position (1.0ms)
    }
    else if( !(P1IFG & 0x20) )          // Button at P1.5 pressed
    {
      TA0CCR1 = 2000;                  // Servo in maximum position (2.0ms)
    }
    P1IFG = (0x08 | 0x10 | 0x20);
}