Text display that shows NBT number tag or local variable?

Hi!

I am trying to make a GUI or Overlay that shows me information about a block.

Example would be: If I click on a block with testing item(Item that opens specific GUI) that Item gets information(specific NBT tag) from the block and than that information is displayed in GUI. Item gets energy_value NBT number tag form block and its displayed in GUI, if clicked on another block that contains energy_value, GUI displays different value.

Key problem is if I can display NBT information in a text_field like "Text is <TextFieldName:text>" without using GLOBAL Variables?

Please comment if you have any Idea of thought about this. Thanks, Kris!