Calculation to get latest completion Date

Question

hi.. thanks guys for all the info.. it really helped me a lot as a newbie..
i am doing a report as an end-user of discoverer desktop 4. how can i get the highest completion date (table and crosstab format) in my data as follows:
BudgetRef ProjectNo TaskNo CompletionDate
2010-01 PN2600 A1000 Mar-2011
2010-01 PN2600 B1000 Sep-2012
2010-01 PN2600 C1000 Jun-2011
2010-01 PN2665 A1000 Jun-2012
2010-01 PN2665 B1000 Dec-2011
2010-02 PN3005 A1000 Mar-2012
2010-02 PN3005 B1000 Dec-2013
2010-02 PN3005 C1000 Dec-2012
Result should be:_
BudgetRef          ProjectNo    CompletionDate
2010-01 PN2600 Sep-2012
2010-01 PN2665 Jun-2012
2010-02 PN3005 Dec-2013
thanks again for the usual assistance.

Answer 1

thanks Michael.. it works fine..
another thing :-).. i tried to run the same report but adding some fields.. comparing the original completion from amended completion but it seems it is giving me a null value if one of the ProjectNo completion date is empty or if the completion date is a text (ie "hold"), and in some cases it is not showing as a line item therefore affecting the ProjectCost
if the comparative completion dates in the original and amended are either empty or is a text.. it should still show the field either an empty field or the text "Hold" (text has the priority when being compared to an empty field) so as to retain the total Project cost.
my sample data are as follows:
BudgetRef ProjectNo     TaskNo     ProjectCost     OrigCompletionDate     AmendedCompletionDate
2010-01 PN2600     A1000     1,000      Mar-11     Mar-12
2010-01     PN2600     B1000     5,000      Jul-10     Oct-13
2010-01     PN2600     C1000     6,000      Hold     May-14
2010-01     PN2665     A1000     3,000      Jun-12     Apr-13
2010-01     PN2665     B1000     2,000      "Null"     Dec-11
2010-02     PN3005     A1000     4,000      Mar-12     May-15
2010-02     PN3005     B1000     9,000      Hold     May-15
2010-02     PN3005     C1000     7,000      Dec-12     Jun-13
2010-03     PN3007     A1000     8,000      "Null"     "Null"
2010-03     PN3007     B1000     2,000      Hold     "Null"
2010-04 PN3008 A1000 _5,000_ "Null" "Null"
          Total     *52,000*           
The result should show as follows:                         
BudgetRef     ProjectNo     ProjectCost     OrigCompletionDate     AmendedCompletionDate
2010-01     PN2600          12,000      Mar-11     May-14
2010-01     PN2665          5,000      Jun-12     Apr-13
2010-02     PN3005          20,000      Dec-12     May-15
2010-03     PN3007          10,000      Hold     "Null"
2010-04 PN3008 _5,000_ "Null" "Null"
          Total     *52,000*           
thanks again for the never ending assistance.