you can't combine the events, like alkohol1k said you'll have to do the events seperatly and echo them to the same window

on 1:FILESENT:*:{ /window -nk[N] @DCC.Info
/echo @DCC.Info $timestamp *** DCC Send Complete to $nick $filename
}

on 1:FILERCVD:*:{ /window -nk[N] @DCC.Info
/echo @DCC.Info $timestamp *** DCC Get Complete from $nick $filename
}

on 1:SENDFAIL:*.*:{ /window -nk[N] @DCC.Info
/echo @DCC.Info $timestamp *** DCC Failed to send to $nick $filename
}

on 1:GETFAIL:*.*:{ /window -nk[N] @DCC.Info
/echo @DCC.Info $timestamp *** DCC Failed to get from $nick $filename
}

and you can add in an else if statement to all of them if the window is already open