Enable and disable dropdown items

[rup1234]

I have a drop down in cell h1 which contains two items like

H1:Wires
Cables
If user click on wires then it would show only wires items and vice versa

For instance

Wires Cables
a 3
b 4
c 5

User click on wires then it would show only a b c

 

[AlphaFrog]

What is "it"?

Are you asking about how to create Dependent Dropdown Lists? If yes, here is a step-by-step guide...
Create Dependent Drop Down Lists