When using 4Spell with e.g. 4TeX is can be useful to check if the file that is currently loaded in the 4Spell editor has changed contents. This is necessary if you would press, e.g., the Compile button in 4TeX. To make this possible 4Spell accepts a DDE command:
4Spell checks if the filename passed as the DDE parameter matched the file currently loaded in the 4Spell editor. If so, and if the content of the file has been changed in the 4Spell editor, the file is automatically saved.