If MYOB is exporting data in the US format, then Excel will convert
some of the
data to Australian format and leave some of the data as text.

If you could give some examples of the actual data; and also execute
an
ISTEXT() function on the erroneous data, we could better help.

The problem appears to be with MYOB. You can 'fix' this (at least
generate proper dates in dd/mm/yyyy format) by applying the following
formula (assuming that the MYOB date you want to alter is in cell B4):

=IF(ISTEXT(B4),DATE(RIGHT(B4,4),MID(B4,4,2),LEFT(B 4,2)),DATE(YEAR(B4),DAY(B4),MONTH(B4)))

This checks whether the cell is 'text' (i.e. Excel has been unable to
convert it to a date). If it is text, the formula constructs an
appropriate date by parsing the text string. If the date has been
interpreted as a date by Excel, the formula swaps the month and day to
give the proper date, as MYOB intended.

RC.