"I have a distribution list of 5 cities in cell A1, 5 manufacturers in cell
B1, 5 products category in cell C1, and 5 product list in cell D1."

Now, I want that if I select one particular city in cell A1, then it should
give me options to select manufacturers available in that city only.

Again, when I select one particular manufacturer in cell B1, then in cell C1
it just show me product category produced by that particular manufacturer.

Then, continuing from previous step I select one product category from that
list (cell C1) and then it should give me products list under that category
in Cell D1.

Now, finally selecting an item from the product list in Cell D1, it should
pop up the username in Cell E1.

Now, as far as this username is concerned I know their combination......

So, what I want is that.... when particular city, manufacturer, category and
product is selected it gives me username in cell E1.