Evaluating code blocks in Rebol3 - rebol3

Question

I'm trying to improve the Sliding Tile Puzzle example by making the starting positions random.
There's a better way to do this--"It is considered bad practice to convert values to strings and join them together to pass to do for evaluation."--but the approach I took was to try to generate Rebol3 source, and then evaluate it. I have it generating correctly, I think:
random/seed now
arr: random collect [ repeat tilenum 9 [ keep tilenum ] ]
hgroup-data: copy {}
repeat pos 9 [
curtile: (pick arr pos)
append hgroup-data either curtile = 9
[ reduce "x: box tilesize gameback " ]
[ rejoin [ { p "} curtile {" } ] ]
if all [(pos // 3) = 0 pos != 9] [ append hgroup-data " return^/" ]
]
print hgroup-data
...outputs something like:
p "4" x: box tilesize gameback p "5" return
p "3" p "7" p "1" return
p "2" p "8" p "6"
...which if I then copy and paste into this part, works correctly:
view/options [
hgroup [
PASTE-HERE
]
] [bg-color: gameback]
However, if I try to do it dynamically:
view/options [
hgroup [
hgroup-data
]
] [bg-color: gameback]
...(also print hgroup-data, do hgroup-data, and load hgroup-data), I get this error:
** GUI ERROR: Cannot parse the GUI dialect at: hgroup-data
...(or at: print hgroup-data, etc., depending on which variation I tried.)
If I try load [ hgroup-data ] I get:
** Script error: extend-face does not allow none! for its face argument
** Where: either if forever -apply- apply init-layout make-layout actor all foreach do-actor unless -apply- apply all build-face -apply- apply init-layout make-layout actor all foreach do-actor if build-face -apply- apply init-layout make-layout actor all foreach do-actor unless make-face -apply- apply case view do either either either -apply-
** Near: either all [
word? act: dial/1
block? body: get dial...
However, if I use the syntax hgroup do [ hgroup-data ], the program runs, but there are no buttons: it appears to be somehow over-evaluated, so that the return values of the functions p and box and so on are put straight into the hgroup as code.
Surely I'm missing an easy syntax error here. What is it?

Answer 1

First, I would say it's better to construct a block directly, instead of constructing a string and converting it to a block. But if you really want to do that, this should do the trick:
view/options compose/only [
hgroup (load hgroup-data)
] [bg-color: gameback]