in imfile, can you filter a multiline comment from the start of the file?

I am reading windows dns logs, and at the start of each file, windows adds text at the beginning of each file. Note that windows will do this in the middle of a multiline log message. Ideally what I want is that when the file is opened, im_file will throw away the header and then pass the rest of the file to xm_multiline so that xm_multiline never knows that this was there. As a work-around I could add a bunch of filters to match each known bad line and throw it out, but that's a pretty inefficient way to do things, This would be something similar to onEOF but happen at the start of the file instead.

an example is:

DNS Server log file creation at 11/6/2019 6:19:22 PM
Log file wrap at 11/6/2019 6:19:22 PM

Message logging key (for packets - other items use a subset of these fields):
Field # Information Values
------- ----------- ------
1 Date
2 Time
3 Thread ID
4 Context
5 Internal packet identifier
6 UDP/TCP indicator
7 Send/Receive indicator
8 Remote IP
9 Xid (hex)
10 Query/Response R = Response
blank = Query
11 Opcode Q = Standard Query
N = Notify
U = Update
? = Unknown
12 [ Flags (hex)
13 Flags (char codes) A = Authoritative Answer
T = Truncated Response
D = Recursion Desired
R = Recursion Available
14 ResponseCode ]
15 Question Type
16 Question Name

normal log data, potentially starting in the middle of a log