Refresh a Show and Hide expression

Refresh a Show and Hide expression

Hello,

     I have the following script:

if((input.Order_Type  ==  "Diet"))
{
    show Choose_Diet;
    show Diet_Description;
}
else if((input.Order_Type  ==  "Medical Equipment"))
{
    show Medical_Equipment_Type;
}
else if((input.Order_Type  ==  "Medication"))
{
    show Medication;
    show Dose;
    show Frequency;
   }
else
{
    hide Choose_Diet;
    hide Medical_Equipment_Type;
    hide Diet_Description;
   }


This seems to work, but when I am in the form it only works one time.  I think I need the form to be refreshed every time a new option is chosen (Diet, Medical Equipment, or Medication), so that the proper options are displayed.  Am I correct in this thinking and if so, how do I do this?

Thanks