how to move a solid body along a clear line
 

hi every body
i am a user of fluent, i have a solid body and i want to move it along a clear line that have not any specific formula to describe it's velocity.
therfore i want to move this solid body along a clear line that i draw it in a gambit, but i dont know how should i define this line in a udf and how define that the solid body should move along this line.
It is noteworthy that my solid body have a constant velocity in x direction but the other velocity component is variable and the udf should calculate acoord with the clear line that i former specified.
can any body help me?