I need help regarding, dropdown , textbox and buttons

Hello mates, 

I have attached a test file and I want solution of following 

1.

                  if dropdown.value="N/A", then textbox.value=" ",

                  if dropdown.value="0", then textbox.value="0%,

                  if dropdown.value="1", then textbox.value="25%,

                 if dropdown.value="2", then textbox.value="50%,

                if dropdown.value="3", then textbox.value="75%",

                if dropdown.value="4", then textbox.value="100%,

2. value in dropdown should be in center rather than left side

3. when I move to next dropdown then it shouldnt allow unless entry of last textbox/dropdown is not made

4. print command should be enabled after entries of all textboxes/dropdown lists

5. clear button should clear all the filled textboxes/dropdown values.

would be thankful for helping me in this regard.