what i can do better ??

Hi,
I need your piece of advice. I am kind of novice to programming C. I am trying to create a Generic LCD_printf function, that can print decimals, string, characters.

The following is the code i am trying

#include <all necessary h file>

// declaration
void lcd_printf (const char *,...);

//definition
void lcd_printf(const char *identifier, const int idata *datastring)
 {
char id;
while  (*identifier !='\0')
{
 if (*identifier == '%')
        {
                identifier++;
                id = *identifier;
                switch (id)
                        {
                                case 'd' :
                                                dectolcd(datastring); // converts decimal to                                             string
                                                break;

        }               }
 else
        {
        _lcd_data(*identifier); // prints the character in LCD
        }
identifier++;
}
 }

void dectolcd(int *datastring)
  {     char *temp;
        sprintf(temp,"%d",datastring); // converts decimal to string
        lcd_display(temp);   // prints string on the lcd
  }

Void main
{
lcd_printf("%d",123);
}

Now when I run this code, I am not getting the 123 on the LCD. I know i am messing with the pointers somewhere. Can someone help as what i can do better ??