parameters with comments

Hi,

I want to create a check box with some long text and also need to do validations

based on the one of the input fld.

for example

there is a fld in the selection screen,

paramaeters: xyz type c (will accept y or n) only.

here the checkbox should come with soem long text.

this check box need to take the value if the above xyz value if 'n' only.

Please provide me the code if possible.

Thanks in advance