Enable textbox

I have an asp page which allows users of the system to enter in new contacts.

If the user chooses option A from a drop down I want to enable a textbox and a dropdown else I want to disable them.

Can anyone point me in the right direction. My understanding of client side script isn't as good as my server side but I dont want to do the round trip.

Thanks in Advance

Try using the visable property, you'll need to either use Style Sheets or the Style tag. Then use the event from the drop down to run some javascript that will change this visable property.