Use Shell Command to sort file In Visual Basic

I have this trouble to use shell command to sort a simple text file from Visual Basic:

Here is the Visual Basic code:

Private sub CmdSort_click()
dim StrCommandLine as string
StrCommandLine=App.Path & "\Zsortsum.bat"
shell strCommandLine, vbMinimized
end sub

The batch file "Zsortsum.bat" is following:
c:\winnt\system32\sort.exe <c:\smy.tmp> c:\sumdoc.srt

The problem is that I can not get the file
sumdoc.srt generated ( or created) after I executed the Visual basic program( there is not error message in VB) . I can have the sumdoc.srt file generate if I use the batch file in DOS system. Could you tell me why? Thanks a lot!!!