Batch Convert FLV to MP4 Then Delete the FLV file

[drbmn]

I'm currently trying to make a .bat file to convert FLV (from rtmpdump) to MP4 using FFMPEG then after the FFMPEG command has completed delete the .flv files on a Windows based machine. I've got this so far but it doesn't seem to delete the files afterwards.

start cmd /k for %%a in ("*.flv") do ffmpeg -i "%%a" -acodec copy -vcodec copy %%~na.mp4
start cmd /k timeout 10 for %%a in ("*.flv") do del "%%a"

anyones help/input would be greatly appreciated.