Check variable with condition to set title text

[#1]

I know the following is wrong, but just to give an idea what I tried to achieve. I have a variable in VBA Macro called 'key'. I want to test the value of the 'key' in the title text in order to populate a title caption. What is the correct syntax?

[#2 · Accepted solution]

Find answer myself:

define variable Select_Key in document properties

set v = ActiveDocument.Variables("Select_Key")

v.SetContent key, true

Then will be able to use $(Select_Key) in the if statement.