Help with Assembly Language Program

Hey guys,
I have this program which is not working. I have been working on it for sometime.. I mean just staring at the code to see if it makes sense. And I havent got any help to go to see if it works. If you could help me it would be really helpful. Its is an 80*86 problem. Here is the code for it. It is really urgent. It was due last week but I havent been able to work it out. I use Windbg to debug it . But it doesnt like something I m doing here. I have added a few lines of code too just for outputing.


;Puneet Kulkarni
;CS 301 assignment 4
.386
.MODEL FLAT

ExitProcess PROTO NEAR32 stdcall, dwExitCodeWORD

INCLUDE io.h ;header file for input/output



cr EQU 0dh ;carriage return character
Lf EQU 0ah ;line feed

.STACK 4096 ;reserve 4096-byte stack
.DATA ;reserve storage for data
prompt BYTE "PLEASE ENTER THE NUMBER YOU WANT TO ADD AND ENTER A NEGATIVE NUMBER TO EXIT",0
prompt1 BYTE "Please enter an integer: ", 0
string BYTE 11 DUP (?),0
Num1 Byte 11 Dup(?),0
Num2 Byte 11 Dup(?), 0
Num3 Byte 11 Dup(?), cr,Lf,0
nums WORD 60 DUP (?)
Orig Byte 11 DUP(?),0
.CODE
_start:
output prompt

lea ebx,nums ;get address of the nums array
Startingpoint:

mov cx, 0
mov dx,0
inc cx
inc cx
output prompt1
input string, 10
cmp string,0
jng finalstart
atod string ; put input in eax
dtoa Num1,eax
output Num1
mov [ebx],eax
dtoa Orig,eax ; moves the value in Orig


lowerloop:
mov cx,2
sub ax, 1
jmp lowerprimetest

lowerprimetest:
mov dx,0
cmp cx, ax
je lowerprime
dtoa Orig,eax

div cx
cmp dx, 0
je lowerloop
inc cx
atod Orig
jmp lowerprimetest


lowerprime:
dtoa Num2,eax
Output Num2
mov [ebx],eax
jmp highestloop


highestloop:
add ax,1
jmp higherprimetest

higherprimetest:
mov dx,0
cmp cx, ax
dtoa Orig,eax
je higherprime
div cx
cmp dx, 0
je highestloop
inc cx
atod Orig
jmp higherprimetest


higherprime:
dtoa Num3,eax
Output Num3
mov [ebx],eax

jmp Startingpoint

finalstart:
lea ebx,nums
mov ecx,0

finalout:
dtoa num1,[ebx]
output num1
dtoa num2,[ebx+2]
output num2
dtoa num3,[ebx+4]
output num3
inc ecx
add ebx,6
cmp ecx,30
je endloop
jmp finalout
endloop:
INVOKE ExitProcess, 0

PUBLIC _start

END