Multiplication and division in x86 MASM

.586
.MODEL FLAT, C

.DATA
oper DB 0 ;Set to 0 if multiplication, 1 if division
a DWORD 25
b DWORD 5

.CODE

MULTIPLY PROC
    mov ebx, 1 ;Move 0 to EBX register for counter
    mov eax, a

    cmp oper, 0
    je multi
    jmp divi

    multi:
        add eax, a
        inc ebx
        cmp ebx, b
        jl multi
        jmp endSect

    divi:
        sub eax, b
        inc ebx
        cmp eax, 1
        jg divi
        mov eax, ebx
        dec eax
        jmp endSect

    endSect:
        mov eax, eax
MULTIPLY ENDP

END