I struggle to understand, from your description, exactly what your problem is. But in order to add text into a #text cast member you might use:
member("text").text = member("text").text && "some more text"
If text cast members contain numbers you can simply add the members text properties together. For example assuming
the text of member(1) is 1
the text of member(2) is 5
the text of member(3) is 10
Type this into the message window
put member(1).text + member(2).text + member(3).text
press ENTER you get
SInce you are adding scores, I assume you want an integer, so use this
put integer(member(1).text + member(2).text + member(3).text)
While the above suggestion may work, it's always safer to manually coerce values into the types expected before applying operands.
tScore = integer(member("score1").text) + integer(member("score2").text) member("total score").text = string(tScore)