How Do i make a pop-up menu's contents change in 1 cell according to what I have chosen in another pop up menu from another cell

Question

In table 1 I have 4 sets of options under the heading "CATEGORY" which will make up a pop up menu in the first cell. "Slat fencing", "standard pool fencing", "Non standard pool and garden fencing" and "Louvres" if I choose one of these 4 categories from a pop-up menu I need the next column to indicate another set of pop up menu's that change according to the first cell that I chose. I.E. I have 2 cells in a table. If I choose "Standard pool fencing" from a pop up menu in the first cell I need the pop up menu in the second cell to show the options Flat top Black, Flat top other colour, Semi frameless glass, Frameless glass.
Any help would be greatly appreciated.
Regards, Brendan.
TABLE 1
CATEGORY
SUB CATEGORY
Slat fencing
Aluminium privacy screens
Knotwood timber grain
knotwood standard powder coated
Standard pool fencing
Flat top Black
Flat top other colour
Semi frameless glass
Frameless glass
Non standard pool and garden fencing
Flat top
loop top
rod top
loop and spear
rod and spear
level spear
hi/lo spear
florence
mondello
venice
sorrento
carini
verona
milan
Pisa 2
Pisa
Meditteranean
Pescara
Louvres
fixed horizontal louvre 85mm elliptical blades
operable horizontal louvres
Vertical louvres (Stefmar) using 65x16 aluminium slats
160mm vertical louvres
TABLE 2
CATEGORY
SUB CATEGORY
Slat fencing
Knotwood timber grain

Answer 1

Brendan,
Let me try to explain using a similar but different method:
All the lines are shown for information flow and would not normally be included.
The table in the top left is a working table where you interact with the information:
You first select a category using a slider.  As you slide left and right the "value" (shown as 2 in column B) will change.  As the value changes the Category changes because the information is looked up from the category table (highlighted with a blue shaded background in the first picture.
The subcategory will also change as you modify the slider in column "B" because you are changing the category, which selects which table is used for the sub-category (sub-category tables are highlighted in light green).  Once you select the category you can then slide through the possible selections for the subcategory (column "D").
There are only two formulas and they are in the "Work" table:
A2=IFERROR(VLOOKUP(B2,Category :: A:C, 2, FALSE), "<Not Found>")
C2=IFERROR(VLOOKUP(D2, INDIRECT(A2),2,FALSE), "<NOT FOUND>")
For A2=IFERROR(VLOOKUP(B2,Category :: A:C, 2, FALSE), "<Not Found>").... this means in cell A2 enter the text "=IFERROR(VLOOKUP(B2,Category :: A:C, 2, FALSE), "<Not Found>")" omit the first and last double quote
This whole scheme requires the tables be named the same as the categories in the "Category" table
I hope this helps.  If not please indicate what is causing you trouble.