case when then

 Hi, I download the following script print out the usage of the current tablespace in oracle db. how do I make the change to only print out any tablespace with pct_used above 70%, instead of print out everything ? thanks.

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REM
REM Script: ts_used.sql
REM
REM Function: Display tablespace usage with graph
REM
REM
column tablespace format a20
column total_GB format 999,999,999,999.99
column used_GB format 999,999,999,999.99
column free_GB format 999,999,999.99
column pct_used format 999.99
column graph format a25 heading "GRAPH (X=5%)"
compute sum of total_GB on report
compute sum of used_GB on report
compute sum of free_GB on report