Bob,
Welcome to QuickBase. It is a great program.
Just to add some colour to the post above, if you want to be able to have a conditional drop down based on first selecting type then the post above from Sam is the correct answer for your use case.
But if in fact you always only want to see companies from companies of type A in that drop down, then you simply build a relationship where one company has many form records and you will have an opportunity on the form properties for that company selection field to choose the report which is used for the drop-down list. If you make a report which simply has a filter for only Type A then the drop-down will always only contain company type A.
