The attached illustrative draft creates a tab-delimited text file (on the Desktop). You should be able to control-click it and choose to open it with Excel. (Or use a Quicksilver "Open With" action).

If you save it as an .XLS file, you will then be able to open the latter in Filemaker. (Trying to open the text file directly in Filemaker will lead to problems with any task names that span several lines).

This draft gives a path number to each task (to represent the nesting) and adds the main dates and other properties after the task name. It should not be too difficult to add further task properties by inspecting and extending the code.