hi;
here is easiest;
mov r5,#xyz;load your multiple
250_ms:
mov r6,#0fah
1_ms:
mov r7,#0fah
loop:
nop
nop
djnz r7,loop
djnz r6,1_ms
djnz r5,250_ms

beware this is busy wait and won't allow anything other than isr to work.if
its not ok then timer solutions which best in any case must be used.
regards
pranav