How to add leading zeros ?

Hi Friends,

I have a shipment no say 10 char long . Now the thing is in my program I need to add leading zeros if the shipment no is not 10 char long .

For eg : if the tknum is 99919 . I need to make use of a command to make it 10 char long lke 0000099919.

Also I need to be able to add zeros if tkum is 5 or 7 or 8 char long .

How do i add these leading zeros to fill up the remaining positions ?

Thanks,