=DATE(YEAR(A1),MONTH(A1)+1,DAY(A1))

When using this to get the next month, find some problem when at end of a
long month (with 31 days), the result came back is the first day of 2 months
later. eg a1=31/3/2008 the result will be 1/5/2008 and not the expected
30/4/2008.

Any way to make it consistant to display end of month

Thanks