You will find that many shares rise going into the ex div date...

You will find that many shares rise going into the ex div date purchased by those who want the dividend, particularly if that dividend is fully franked. That’s all good, but what you have to try and work out how much the share has traditionally dropped ex div. That’s the hard question. You already know how much dividend they are going to pay, but you don’t know how much more than the 4c dividend they are going to drop, and how long CDM will take to recover that, by which the share will drop. Re future dividends… go to your broker site and look at the dividend history for a possible answer.