Flat File load

I have a flat file from which I need to get a date from the first line and load the data from the other lines. My thought was as follows, could someone confirm that this is feasible and/or an alternative/better solution? Thanks

1) In the comm/transfer structure create a field for the date populate this via a routine (this is always the same for each load i.e. is the same value in the header line). If this is feasible can someone advise me on the logic

2) Load the other comm/transfer structure fields via one to one mapping

Or will I have a problem since the file has a header line which is different in structure to the detail lines?