problem placing 3 bytes in a variable and divide it

hello, i now have 3 bytes that need to place as first byte,second byte and third byte in a variable then converted into a decimal number ,
but the result is 0, can anyone help
supposely the b1,b2 and b3 for me is variable

#include <stdlib.h>

unsigned char fb,sb;
unsigned int count,size;
unsigned long packages,temp,b1,b2,b3;
float temppack;
char pac_show [sizeof(unsigned long)*8+1];

void main(void)
{
	b1 = 0xF5;
	b2 = 0xCE;
	b3 = 0x12;
	temp=b1;
	temp<<8;
	temp+=b2;
	temp<<8;
	temp+=b3;
	temppack=temp/506;
	packages = (unsigned long) temppack;
	ultoa(packages,pac_show,10);
	LCD_sendstring(pac_show);
}

problem is there, make the following changes..

temp=b1;
temp=temp<<8;
temp=temp+=b2;
temp=temp<<8;
temp=temp+=b3;

you forgot to store temp after shifting