I have a form to collect equipment category name. eg. Dryer, Heater, Cooler etc....

Form Name - 'Add Equipment Category"

Field Link Name - "Equipment_Category"

Then, I have a form where equipment names are being collected and each of them are being mapped to their equipment category by a lookup field. eg. Heating Coil mapped to Heater, Pump mapped to Cooler, Control Valve mapped to Dryer etc...

Form Name - "Add Equipment"

Field Link Name (for equipment name) - "Equipment_Name"

Lookup Link Name (for mapping equipment category) - "Add_Equipment_Category"

Now in another form, an user in creating an order and adding equipment category and equipment name.

For this the form has a user field for input of Order Number 

Next, there is a Lookup for selecting Equipment Category ( Lookup Name - "Select_Equipment_Category")

And another Lookup for selecting Equipment Name (Lookup Name - "Select_Equipment")

What I am looking for is way so that when an user select a certain equipment category in the first Lookup (Select_Equipment_Category), only those equipment mapped / assigned to that particular equipment category will be available to select on the next Lookup (Select_Equipment).