enabling/disabling fields based on value selection in the list box

hi folks

i am working on requirement where i have 7fields on my web ui.i have a list box and in the list box there are 2 values.now if the customer selects the value '1' in LB then fields f1,f2,f3,f4 should be visible and in editable mode and if value '2' is selected then f5,f6,f7 fields should be visible in editable mode.

i created list box and populated the values now how can i achieve the next functionality?

regards

sap