File in use status for FTP

Hello All,

I've one application developed in VB.NET which uploads the file (i.e zip) on FTP Server. It takes around
20 Seconds to upload that file. Application uses Binary mode to transfer the file. Now at the other end
one applicaton (It also uses binary mode to download file) simulaneoulsy accesses the FTP to check any
new file is there and if so the download that file to local machine. Now query is that when one applicaton
is uploading file to FTP and at same time other application tries to download file it downloads the incomplete
file (i.e still uploading is in progress at other end)

So query is that how can I get status of FTP that particular file is in use? So when I try to download file
I'll always get complete file. Is there any other way to achieve this functionality (i.e one application checks
FTP Server at particular interval and it should start download at only that time when it finds complete file.)


Thanks in advance and any help appreciated.