Select ROW_COUNT() INTO a variable

[Bryan Cantwell]

I have a stored procedure in mysql 5.1.48 that deletes old data from my
tables.
I would like to keep a running count while it does this. Here is what I
try now:
...
DECLARE dropCnt INT DEFAULT 0;
...
SET @sql = CONCAT('DELETE FROM  myTable WHERE itemid = ', iID, ' AND
clock BETWEEN 0 AND ', histUnixTime, '  ');
                  PREPARE s1 FROM @sql;
                  EXECUTE s1;
                  SELECT ROW_COUNT() INTO dropCnt;
                  DEALLOCATE PREPARE s1;
...

The problem here is that "SELECT ROW_COUNT() INTO dropCnt;" returns NULL
every time.
If I just do the select without the INTO, I get 0 or some actual count
of rows. 
How can I get my dropCnt variable correcly set?

Thanks,
Bryancan