As far as placing var in text strings is rather straight forward but will require a bit of labor.
var "Apple_Red" = 10
Start of Layout > Set text for Textbox to "Have you collected all the apples?"
If Yes_btn is clicked
"Apple_Red" >= 8
set Textbox to "Great now I can make that pie"
"Apple_Red" < 8 then
set Textbox to "Oops, You need to collect "& 8-"Apple_Red" & "Red Apples. Please look for them"
So it can be done but you need to edit the string to have the variable in it instead of a string. '&' is what you use to bind two things together so all you need is to have "The text string" & variable & "last text string."
"Were all mad here. I'm mad, your mad." "How do you know I'm mad?" Asked Alice. "You must be" Said the Cheshire Cat. "Or you wouldn't have come here"-Lewis Carroll: Adventures In Wonderland