It's easy to fix

lcStr = "W-4568E5B"
lcNum = CHRTRAN(lcStr, CHRTRAN(lcStr, "0123456789",""),"z")
DO WHILE NOT ISDIGIT(lcNum) AND NOT EMPTY(lcNum)
	lcNum = SUBSTR(lcNum,2)
ENDDO

>This will also fale on for instance lcStr = "W-4568E5B"
>
>
>>

>>lcStr = "W-4568S5B"
>>lcNum = lcStr
>>DO WHILE NOT ISDIGIT(lcNum) AND NOT EMPTY(lcNum)
>>	lcNum = SUBSTR(lcNum,2)
>>ENDDO
>>
>>? INT(VAL(lcNum))
>>