you can use the ctcp that gets sent when any dcc is going to attempt to transfer and setup a timer based on it..

ctcp *:DCC SEND*:{ if ($7) { echo -s Attempting transfer of $3 to $nick } }

the if ($7) is because the same "dcc send" ctcp is sent to you both when the other user is confirming your dcc send to them, or initiating a dcc send to you. there is 6 total fields when the other person is initiating a send, and 7 total fields when they are confirming a send initiated by you.