Are you referring to differentiating the project to meet all of your students' needs? If so, using a rubric is helpful. You can create separate rubrics (2 or 3) that fit the learning needs of your students. Make one for your high achieving students, one for your moderate students and one for your low students.
However, I've found that the more that I push my students to achieve greater things, the more that they rise to the occasion. Without more specifics about the project, it is hard to give more feedback. Good luck!