Storing expression references to data base

Question

I have standard arithmetic expressions sotred as strings eg. "WIDTH * 2 + HEIGHT * 2"

In this example WIDTH and HEIGHT references other objects in my system and the literals WIDTH and HEIGHT refers to a property (Name) on those objects.

The problem I'm having is when the Name property on an expression object changes the expression won't match anymore.

One solution I came up with is to instead of storing

"WIDTH * 2 + HEIGHT * 2"

i store

"{ID_OF_WIDTH} * 2 + {ID_OF_HEIGHT} * 2"

And let my parser be able to parse this new syntax and implement an interface or such on referenced objects

IExpressionReference
{
  string IdentifierName { get; }
}

Anyone have a better/alternative solution to my problem?