Here is a snippet I made for the VScript File Replacer that sets the cans required from the value of a ConVar (mine is named "l4d2_cans" in this case).
Code:
"c1m4_atrium"
{
"c1m4_atrium_finale"
{
"NumCansNeeded <- 13" "NumCansNeeded <- Convars.GetStr(\"l4d2_cans\").tointeger()"
}
}