I'm not familiar with the Game Book version, so I'm not sure how the page links work/are-set-up, but this is the concept:
let's say that 'page10' Page takes you to 'page15' Page, unless you've already encountered 'page 30' Page, in which case, 'page10' Page will take you to 'page99' Page:
'page10' Page -> Page Type -> [script] or [text+script]
run as script -> add new script -> scripts -> 'if' Script -> [EXPRESSION] and type/code it in yourself (see below), or whatever correct [xxx] option instead
if [EXPRESSION] page30.visited
run as script -> add new script -> variables -> 'set a variable or attribute' Script -> [EXPRESSION] and type/code it in yourself (see below), or whatever correct [xxx] option instead
// for the 'if true' action:
set variable player.parent = [EXPRESSION] page99
// for the else (if false) action:
set variable player.parent = [EXPRESSION] page15
in code example:
if (page30.visited) {
player.parent = room99
}
else {
player.parent = room15
}
the Game Book version, may not have the 'visited' built-in Boolean Attribute, so, in which case, you'd have to create your own Boolean Attribute and set it up and handle it correctly.
also, again, the Game Book version may not have/use the 'parent' Attribute and/or no the 'MoveObject' Script/Function for determining what page to be-at/move-to