msbox() function with vb like sytax and constants

Example
i as integer
i = msgbox("Do you want to Exit?",MsgYesNo+MsgCritical,"Quit")
if i = MsgNo then wait 500
until i = MsgYes

                                    ` This code was downloaded from The Game Creators
                                    ` It is reproduced here with full permission
                                    ` http://www.thegamecreators.com
                                    
                                    `vb style msgbox function
`
`include in project and call like
`i as integer
`repeat
`i = msgbox("Do you want to Exit?",MsgYesNo+MsgCritical,"Quit")
`if i = MsgNo then wait 500
`until i = MsgYes
`
`Based on vb msgbox function, see vb help or google for vb msgbox for usage info
`or see this site.
`http://www.w3schools.com/vbscript/func_msgbox.asp
`
`Optional constants, rem them out if you don't use them.
`opts (button) constants
#constant MsgOKOnly           = 0
#constant MsgOKCancel         = 1
#constant MsgAbortRetryIgnore = 2
#constant MsgYesNoCancel      = 3
#constant MsgYesNo            = 4
#constant MsgRetryCancel      = 5
`
#constant MsgCritical         = 16
#constant MsgQuestion         = 32
#constant MsgExclamation      = 48
#constant MsgInformation      = 64
`
#constant MsgDefaultButton1   = 0
#constant MsgDefaultButton2   = 256
#constant MsgDefaultButton3   = 512
`
#constant MsgApplicationModal = 0
#constant MsgSystemModal      = 4096

`return values
#constant MsgOK     = 1
#constant MsgCancel = 2
#constant MsgAbort  = 3
#constant MsgRetry  = 4
#constant MsgIgnore = 5
#constant MsgYes    = 6
#constant MsgNo     = 7
`remend

function msgbox(msg as string,opts as integer,title as string)
`returns -1 if fail (all dll slots taken)
local dll_num as integer : local hwnd as integer
local response as integer
dll_num = free_dll()
if dll_num > 0
  load dll "user32.dll",dll_num
    hwnd = call dll (dll_num,"GetActiveWindow")
    response = call dll (dll_num,"MessageBoxA",hwnd,msg,title,opts)
  delete dll dll_num
else
  response = -1
endif
endfunction response

function free_dll()
local i as integer : stop as integer
repeat
  inc i
  if i < 256 then if dll exist(i)=0 then stop = 1
until stop = 1 or i > 255
if i > 255 then i = 0
endfunction i