qry in calendar control

[srivalli]

hii
in my form i placed one calendar control(is web control)
suppose i selected sysdate from the calendar control
now i want to subtract the current date or sysdate and i want to store the subtracted date starting day and ending day

for adding dates using calendar control,
we use calendar1.selecteddate.addmonths(3)
lllry i want to know it for subtracting

and parameters needed to subract the date from calendar control.
thanks