Question about Mapping Flat File

I have a fixed width flat file that looks something like this:

     Field1  Field2  Field3   Field4  Field5

I want to normalize the data so that Field2 and Field4 become node levels 
and get something like this

     <Order>
	Field2
	<parts>
		Field4
		<requirements>
			Field1
			Field3
			Field5

I don't see a way in a map to tell it to create a new node when the value
in 
Field2 changes.

We're thinking about creating a custom pipeline so that we can parse
through 
the file in VB and reformat it that way. I'm hoping some of you might be
able 
to provide simpler alternatives.
-- 
Ellen Deak