You need to define variables using the define command and then use the format command.
Consider the example below where two variables are defined by define command
– 1st sets the directory location and 2nd sets the file name. These variables are then used in the TUI command by using the format command.
Here the TUI command writes a mesh file to the specified directory and file name. Note ~a ~a is replaced by the variable values.
(define dir_name “/temp/box/bit/”)
(define file_name “mesh1.msh”)
(define command (format #f “file/wm ~a/~a” dir_name file_name))
(ti-menu-load-string command)