[ns] getting values from trace file during execution of tcl script

Hi,
during execution of tcl script, is there some way to get values from trace
file (e.g number of sent packets) after a specific time interval (e.g.3ms)?
I need to write a function to count number of sent/received packets or
bytes after every 2ms.

I hope many researchers are present at this platform so plz consider it and
do reply me.

Thanks in advance

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Regards