2 dropdown List use in gridview

I have 2 dropdown List , the first one contains a list of categories and the secon one contains subCategories.

How can I choose an item from the First List and then display only subcategories in the second one .

I have my tables in WFGEN Database and I created two global Lists.

I want to use it in GridView,I can use from.But it won’t be used GridView

How to use it? Is there a case,thank you

Best Regads,

(sorry for the double answer)
You have to make a restriction on your 2nd drop down list with the value of the first drop down list :

In the part in yellow, you have to indicate your 1st drop down list.

Best regard