Locate Data & Flag If Not Present

I have 2 named ranges that are one besides the other - let's name them tTableA and tTableB. I also have a strValue, which holds a String I will be searching for in tTableA.

Now, tTableA contains names (strings), while tTableB contains quantities (numbers) for the corresponding names.

I need a Button that, when clicked, will do this:

1) Check to see if the strValue string is present in tTableA:
1.1 If NOT present, tell the user "Error".
1.2 If present continue

2) Now that we know strValue exists in tTableA, find the corresponding quantity located in tTableB (this quantity would be on the same 'row' as the row in tTableA which contains strValue)
2.1 If quantity <= 0 then tell the user "Nothing left"
2.2 else REDUCE that quantity by 1 unit.