Crystal Reports Previous /Actual / Future Dates

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     Hi Everybody , im a newbie in CR  and facing the following problems : 

We suppose we have the 4  following Dates ( as at 07/09/ 10 ) coming from the table EVENTS ( EVENTS_DT to be precise) ,i want to extract  the last previous Date which is 02/08/2010  .

The problem thats is my  below formula called Previous EVENTS_DT 
:if {EVENTS.EFFECT_DT}  <CurrentDate  then  ( previous( {EVENTS.EFFECT_DT}))   so i want to modified accordingly to extract the last date  from 01/07/2010 and 02/08/2010 which is 02/08/2010                  

EVENTS_DT                
01/07/2010                   

02/08/2010
01/09/2010
01/10/2010

Previous EVENTS_DT 

01/07/2010                   

02/08/2010

Now i want to extract with my 2nd  fonction called CURRENT EVENTS_DT the  First EVENTS_DT   to be after Today Date ( 07/09/ 10 ) which is 01/09/2010

Finally i want to extract the Future EVENTS_DT , the one Just Next after the CURRENT EVENTS_DT which is 01/10/2010

Many , many thanks !