Hide/Unhide rows Based on Value from Dropdown Lists

Hi, need help with the following

Cell A3 has drop down list "+" & "-".
If A3 = "+" unhide row A4:A10
If A3 = "-" hide row A4:A10

Attached is a Sample workbook.

Problem 1: I have to click away from cell A3 for the code to work. How can I activate the code just by selecting the item from the list?

Problem 2: I unlocked the cell A3 and Protected the sheet with (select unlocked cell) option. doing that rows can't be hidden or vice versa. I need this to work on a protected sheet otherwise i could have used the group/ungroup from data menu.

Any help will be appreciated. thanks