auto refresh the data to blank if another cell data is changed

Dear all,

i am facing a problem to verify the data accuracy if 1 data is been changed, another data must auto set to blank.


i upload my excel file herewith.

refer to my sheet 1.
i have 2 columns, column 1 and column 2.
column 1 is the category, and column 2 is the items of the category.

for example, if column 1 is choose fruit in the drop down list, the item in drop down list in column 2 will auto display the different type of fruit.
columns 2 data is depends on the category of column 1 select.


my problem is when user select the column 1 and then go to select column 2.
then user go to change the category in column 1 without change the data in column 2.
then 2 column data is not matching.

how to make the column 2 data auto refresh and set to blank when user edit the data in column 1?
or prompt an error message if 2 column of data is not matching?

looking forward from your all.