I need help calculating the time difference between two records based on a 3rd field value.   For instance, I need to calculate the time difference in the below table when the status equals WAPPR and COMP.   Please note these are different rows within a table. I will also need calculate the time difference between other Status changes.

Table:
WONUM     STATUS     CHANGEDATE
TKT9904     COMP     10/16/2014 7:59
TKT9904     REVIEW     10/16/2014 7:59
TKT9904     APPR     10/14/2014 9:31
TKT9904     WAPPR     10/13/2014 11:19
TKT9904     INPRG     10/15/2014 8:01
TKT9904     AUTH     10/13/2014 12:16
TKT9904     SCHED     10/13/2014 12:16
TKT9904     AUTH     10/13/2014 12:17
TKT9904     ASSESS     10/13/2014 11:39

Any Assistance would be greatly appreciated!!

do you need to do additional work with the various results or just display them in the group header or footer?
Can you write or use a stored procedure to get this data?

Some options:
1. if you can sort them in a row sequence that allows you to do calculations off next() or previous() that would be one way.
e.g. datediff('n',table.changedate,next(table.changedate))
2.You can use several formula to get the status value at a group level per status type then do group calculations from those. This assumes you are grouping on WONUM
e.g.
@compdate as: if status = 'COMP' then changedate ELSE '1/1/1900'
group result: max(@compdate,wonum)
repeat for the different types
you can now use these in another formula
datediff('n',max(@compdate,wonum),max(@wapprdate,wonum))
3. use a command or stored proc to get the data in a more friendly column format
-1 option is to use pivot on the various dates
-another option is to join the table to itself and have conditions on the join.

if you need to do additional report summaries on the results the stored proc or command are your best options. You cannot really do more calculations on next/previous results or the group results.