How can I enter a combination of text and cell value coming from a module in a dashboard Text box?
You can't link your dashboard texts to module line items.
You can try creating a text formatted line item in a module (without any dimension) and publish them as a line item in the dashboard.
You can also use this line item for your calculation.
There is no way you can link your TEXT box of dashboard to the backend modules. You can try Populating the Selected Line item to the Dashboard.