Inserting a timed delay in a pl/pgsql procedure

I have a problem right now where the execution time of a scheduled
stored procedure is creating an issue with our background data logging
system.
Initially I thought it may be caused due to table locks or the like, but
after much testing I have ruled that out, since data is being inserted
while the scheduled SP runs.

The problem cause is one over which unfortunately I have no control.
However, I wanted to run a test and see if I cuold minimize the problem
by inserting a delay in the stored procedure so that after each loop of
the data aggregation, it "sleeps" for a second or so to let the
backround logger despool its queue.

I tried the following:

FOR myrecord in select * from tblkstests where stats = true and
accountno=423 LOOP
returndate := fn_calcteststats(myrecord.kstestssysid);
nextexecdate := returndate + interval '0.25 second';
LOOP
EXIT when current_timestamp > nextexecdate;
END LOOP;
END LOOP;

However, it appears that current_timestamp is not being recalculated.
Any ideas? While normally we want the stored procedures to run as
quickly as possible, this is a case where I need to insert a delay.
I guess an option would be to place a counter and loop through it, but
it does not allow me the control I relly need.

I am not sure this will resolve the problem, but it's a start.