You'll need to create another slider call it something like 'function'
Then create a text box and enter something like:
when(1<=function<=1,1)
Calculate this, then store it as function1
Now change your first function to be function1*a*sin(b*x-c)+d...
Now create another text field:
when(2<=function<=2,1)
calculate and store then change function 2 etc...
However I would suggest it would be simpler to create multiple pages, with one page per function...