Referrencing columns by header and from different worksheets
 

I would like to reference a group of data that is on a different
worksheet (call it SHEET2) and then map the data from that sheet by
looking up the HEADER name in that sheet, onto SHEET1. This will need
to be done by looking up a keycode from both sheets.

For example. I am on Sheet1, and on Row 5. Keycode is 12345. (fields
are keycode, field1, field2)
I would like to look up keycode (header will always be there, however,
it might be a different column, than the last time, due to different
export utilities) Sometimes, columns may be ordered Keycode, field1,
field2 the next time it might be field2, field1, keycode.

I then would like to get the value for field2 from sheet2, and paste
that into field2 on sheet1

How would I do this?

Thanks
Bruce