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."