How to set default values and dropdown

I am having difficulty getting this to work. Any help is greatly

appreciated.
I have a user table that has the fields username and areaid
username areaid

stanl 1

ksouth 2

.

.

.

etc.
I have a request table that has areaid, customer, problem
areaid customer problem

1 john need computer

1 joe need network

2 sue word document problem

.

.

.

etc.
When user stanl signs on for areaid 1, how do I set the default value for areaid to 1

and likewise areaid 2 when ksouth signs on for area2? I do not want the user to have to pick their area
area 1 does not see area 2 records and vice versa
In addition I have a dropdown for building that is tied to the area, so when area 1 is signed on

you only see buildings for area 1. The table is simply building and areaid. How do I populate this

using the areaid of the user signed on so I only get building for their area?
Thanks