I use Scottrade and I can look up any EX-DATE for any stock.
CLM has the next EX-DATE of 9/13/2010 so make sure you own the shares by 9/12/2010, payment will be made on 9/30/2010 with the dividend of .1398 which currently gives a 15.127% yield based on $11.09 PPS.
You also can use the following site to check for the EX-DATES
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