Lpc2000

How do i calculate the time?
I have the example you can see herunder.

In the interrupt routine the TOMR0 is set to 149999 because it 
should be 10mSec.

But how do i calculate the number? if i need a another time.

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void tc0 (void) __irq  
{
  T0MR0 = 149999;                // 10mSec = 150.000-1 counts
  T0IR        = 1;               // Clear interrupt flag
  VICVectAddr = 0;               // Acknowledge Interrupt

	if ((IO1SET & 0xff000000) == 0xFF000000)
		IO1CLR = 0xFF000000;
	else
		IO1SET = 0xFF000000;	
}

/* Setup the Timer Counter 0 Interrupt */
void init_timer (void) 
{
  T0MR0 = 149999;                   // 10mSec = 150.000-1 counts

  T0MCR = 3;                        // Interrupt and Reset on MR0
  T0TCR = 1;                        // Timer0 Enable
  VICVectAddr0 = (unsigned long)tc0;// set interrupt vector in 0
  VICVectCntl0 = 0x20 | 4;          // use it for Timer 0 Interrupt
  VICIntEnable = 0x00000010;        // Enable Timer0 Interrupt
}

int main (void)  
{
	unsigned int i;
	IO1DIR = 0xFFff0000;
	init_timer();
	while(1) 
	{
		IO1SET = 0x00FFffff;	
		for (i = 0 ; i < 1000000 ; i++ ){}		
		IO1CLR = 0x00FFffff;	
		for (i = 0 ; i < 1000000 ; i++ ){}		
	};
	return 0;
}