just create a new variable (select month)
step- create a new input control as Entry field
step2- write a if condition on a chart =If(Match([Select Month];"*jan*")=0;1;0)
Note user has to manual Enter the value
User can enter value like JAN,FEB,MAR etc....
OR user can enter C1,C2,C3,C4...............
THEN YOUR FORMULA BECOME
step2- write a if condition on a chart =If(Match([Select Month];"*C1*")=0;1;0)
THE ABOVE FORMULA WILL HIDE THE CHART 1