Ignore Digits Property on user input

In composer on a user input block. I would like to ignore all digits expect for *. I’ve try the following combination 1,2,3,4,5,6,7,8,9,0 and 1;2;3;4;5;6;7;8;9;0 but neither on of them work, and suggest would be great. What the support doc reads is below.

Ignore Digits Property
Select the variable to contain a sequence of up to two keys to be treated as though the keys have not been pressed

Documentation clearly states why it doesn’t work…
If you want a different treatment you need to create your own grammar and configure it under the input block