INT 6F - 10NET - LOCK HANDLE                                                    
	AH = 07h
	BX = file handle
	CX:DX = starting offset in file
	SI = record length
Return: CF clear if successful
	CF set on error
	    AX = error code (see also AH=00h)
		0002h file not found
SeeAlso: AH=08h"10NET",AH=0Fh,INT 21/AH=5Ch