Another solution inspired by http://blog.bjartwolf.com/?p=4272

problem5_ternaryNumbers.fs

let calcExpr n =
  let rec innerCalcExpr n current last=
    if current>last then "" else  [|""; "+"; "-"|].[n%3] + string current + innerCalcExpr (n/3) (current+1) last
  "1" + innerCalcExpr n 2 9

let rec sum = function
  |(op::h::t) -> (int (op+h)) + sum t
  | _ -> 0
  
let eval text =   sum ("+" :: (System.Text.RegularExpressions.Regex.Split(text,@"(\+)|(-)") |> List.ofArray))

let generateAndPrint() = seq {0 .. (pown 3 8) - 1} |> Seq.map calcExpr |> Seq.filter(fun s->eval s = 100) |>
                         Seq.iter (printfn "%s")

Obviously not the way to do it! :)