Programattically allow user to create field name or alias for a table

Not sure if this is the right place to ask this, but here goes anyway.

I have a relational db with an Items table, and a Values table where the user can enter, using a FormView, Values versus date for any selected item.

In simple form, the  Values table would look like this:

Date       Value     Item_ID

and so if the Item_ID happened to correspond to the Item named Weight, the user enters as the Value, the Weight at different dates. 

But -- some Items have more than one Value associated with them, like Blood Pressure for example. In such a case my Values table would be set up like so:

Date      Value1     Value2      Item_ID

and the user could use put his Diastolic reading in the Value1 position, and the Systolic reading in Value2 position.

THE QUESTION: Different users will w ...