I\'m able to get cells to format as Dates, but I\'ve been unable to get cells to format as currency... Anyone have an example of how to create a style to get this to work?
For at least Excel 2010: Go into Excel. Format a cell they way you want it.

Then go back into the format dialogue. Select custom.

Copy paste the text it has on the top row under Type: into
createHelper.createDataFormat().getFormat("");
Example:
createHelper.createDataFormat().getFormat("_($* #,##0.00_);_($* (#,##0.00);_($* \"-\"??_);_(@_)"); //is the "Accounting" format.
Make sure you set your populate your cells by using a double. Using the index may cause problems with different versions of Excel. Note that the new format you create above ends up in the custom dialogue from step two.