You can add several commands to the 'Tools' menu of TeXnicCenter, that allow you to invoke external tools. This is a very powerful feature. Using placeholders for the 'Arguments', this feature allows you to integrate external tools like spell checkers and other tools which have to work with the current document or currently selected word or elements like that.
To customize the 'Tools' menu, you have to open the customization dialog and select the 'Tools' page.
The meanings of the controls are:
You can create a new entry by choosing the new button (rectangle), remove the selected entry by choosing the delete button (cross) and move the selected entry up or down in the menu by choosing the up or down button.
To change the entry name, simply select an item an press 'F2'.