You would have to look for announcements from each of the component companies in the fund and then weight them by their weight in the fund.
Sig is correct, you would have to weight the dividends of the individual companies that make up the XLE. A lot of work. About the best you can do is to use the dividends from a closely related ETF and use that to approximate the upcoming XLE dividends. For example, VDE the Vanguard Energy ETF, usually posts dividends about 2 weeks before XLE.