javascript

I need help with writing a javascript code for a series of dropdown lists in a fillable PDF document. I want the first dropdown list to determine the options available in the second and third dropdown list. For example, if someone selects 1.1 from the list of available options, they can only select 11 from the second dropdown list and 0010 from the third dropdown list. Another example would be that if the user selects 1.2 from the first dropdown list, they could only select 12, 15, or 16 from the second dropdown list and from a series of options (0020, 0040, 0050, etc.) from the third dropdown list. Can anyone help me with creating these relationships?