working with a Custom Type

hi guys!

I'm not at all familiar with the proper technical names for what I want.... so I'll just demonstrate to you the end result I'm looking for:

What i what is to create a custom type (named Estimation) used in the following way:

Dim EST as Estimation
EST.Type=Robust

Where "Type=" would bring (intellisense) Robust , Adaptive , Standard or NoneStandard as possible constant options to choose from.
The Estimation type has more stuff in it of course, but I'm focusing on this one particular property, in here.

My question is this:
Am I using the wrong object (custom type) where this syntax would be more (or only) typical for a custom Class rather than a custom Type?
Is that why I have not been able to set it (and could never do...)?

I just want a way to save me from explicitly typing "Robust" or "Adaptive" or another ... every time I want to configure the Type property for Estimation, but have an already set of constant choices to choose (to avoid typos and save time..).

Thank you!