User input to Batchmesh criteria and parameter file using TCL/TK

Hello,

Below is the code to take input from user and store to variable $input

I want to run batchmesh script using this mesh size from user input.
Thank You for any help in this regard

set input [hwtk::inputdialog -text 'Enter Average Mesh Size' -inputtype str \
    -x [winfo rootx .] -y [winfo rooty .]]

Also, Can we modify above code to ensure that user inputs only numbers and not text.

Thank You !
Pritish