Making a basic dialog start Maximized and be resizable

A pretty simple question, How do i make the dialog shown below start maximized and be resizable? I can't seem to find a WS_SOMETHING for when i state the size of the dialog in the resource section for either of these. I think i might have to use SendMessage() with something in the WM_INITDIALOG section telling the dialog be maximized before its shown but im not sure. I haven't done any Windows programming for a while now so i'm having to learn it all again Confused

. If someone could just point me in the right direction here that would be great.

Code:

format PE GUI 4.0
entry start
include '../../INCLUDE/win32a.inc'

section '.data' data readable writeable
        flags dd ?
;end of .data

section '.code' code readable executable
  start:
        invoke  GetModuleHandle,0
        invoke  DialogBoxParam,eax,37,HWND_DESKTOP,DialogProc,0
        or      eax,eax
        jz      exit
  exit:
        invoke  ExitProcess,0
;end of .code

proc DialogProc hwnddlg,msg,wparam,lparam
push    ebx esi edi
cmp     [msg],WM_INITDIALOG
je      wminitdialog
cmp     [msg],WM_COMMAND
je      wmcommand
cmp     [msg],WM_CLOSE
je      wmclose
xor     eax,eax
jmp     finish
        wminitdialog:
                jmp     processed
        wmcommand:
                jmp     processed
        wmclose:
                invoke  EndDialog,[hwnddlg],0
        processed:
                mov     eax,1
        finish:
                pop     edi esi ebx
                ret
endp
;end of dialog procedure

section '.idata' import data readable writeable
library kernel,'KERNEL32.DLL',user,'USER32.DLL'
import kernel,GetModuleHandle,'GetModuleHandleA',ExitProcess,'ExitProcess'
import user,DialogBoxParam,'DialogBoxParamA',EndDialog,'EndDialog'
;function imports from WINAPI

section '.rsrc' resource data readable
directory RT_DIALOG,dialogs
resource dialogs,37,LANG_ENGLISH+SUBLANG_DEFAULT,maindialog
dialog maindialog,'Dialog Box',130,50,600,500,WS_CAPTION+WS_POPUP+WS_SYSMENU+WS_MAXIMIZEBOX+WS_MINIMIZEBOX
enddialog
;End of Resource Data