LONDON -- Next week sees more FTSE 100 companies going ex-dividend. If you want to be eligible for a firm's payment, or if you're hoping the shares might drop disproportionately when the time has passed, you need to be aware of the crucial dates.

Here are three FTSE 100 companies going ex-dividend next Wednesday, April 24. None is offering a massive payment, but they're all on the rise.

Old Mutual (LSE:OMU)
Old Mutual is set to go ex-dividend with respect to its final dividend. The payment of 5.25 pence per share was announced on March 1 and takes the life insurance company's total annual payout to 7 pence per share, which is 23% ahead of the 5 pence paid for 2011.

On the current share price of 199 pence, that represents a dividend yield of 3.5%. The latest forecasts suggest respective yields of 4% and 4.5% for the next two years, with the shares on a forward price-to-earnings ratio of 10.

Rexam (LSE:REX)
Packaging-maker Rexam goes ex-dividend on the same day, and again it's a final dividend. This time there's a payout of 10.2 pence per share due, lifting the full-year total by 6% to 15.2 pence -- the firm paid 14.4 pence per share in 2011.

With Rexam shares currently on a price of around 520 pence, that 15.2 pence dividend provides a yield of 2.9%. That doesn't reach the FTE 100 average of around 3.1%, but after the firm slashed its dividend in the crunch year of 2009, it has been steadily recovering -- and we have more growth forecast for this year and next.

Aggreko (LSE:AGK)
Aggreko, the supplier of power-generation and temperature-control equipment, is our third for today, also with a final ex-dividend date next Wednesday. Aggreko's payment of 15.63 pence takes its full-year payment to 23.91 pence per share for a 15% rise on 2011.

In terms of yield, that's a modest 1.3% based on today's share price of 1,791 pence, but Aggreko's dividend has been rising over the past few years. And though earnings are forecast to fall a little for 2013, there is still a further increase of 8% to 9% in the dividend currently forecast by the City.

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Alan Oscroft has no position in any stocks mentioned. The Motley Fool recommends Aggreko. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.