how to appy a transient load when transient function is know in ansys.

hii,

I m doing a project in which i have to apply a transient force in Ansys.The force func is:

force(t)=[1-cos(2*pi*f*t/3)]cos(2*pi*f*t)    for         t =   0 to 3/f

           = 0.0                                                          otherwise

My prblem is that, whether this function is multi valued function based
on the regime value or a single equation?? And again Shall i have to
write separate LS file for each laod step?? kindly suggst me steps to
follow while applying this type of load. i wud be vry thankful to u.