Code:
MOV BL,88
  NEG BL
ROR BL,4
NOT BL
XOR BL,AL
 NOT BL
ROR BL,4
NEG BL
MOV EAX, "start of your code to crypt"
INC BL
XOR BYTE PTR DS:[EAX],BL   <<<<<<<<<<< *theseadress
INC EAX
CMP EAX,"end of your code to crypt"
JLE adress of  *theseadress

<<<<<<<<<<<
any kind of jump to your OEP