So, you want to input box for only numbers, between 0&100. Here is another way. Not the good one but at least it can give some idea;

Code
#include <acknex.h>


STRING* defstr="#100";
STRING* test_str="";


//is input box open
int is_input_box_on=0;

//test variable
int test_num;

//debug
function textx_startup()
{
	while(1)
	{
		if(is_input_box_on==1)
		{
			draw_text("Enter any number",1,1,COLOR_GREEN);
			draw_text(test_str,1,200,COLOR_GREEN);

			
		}
		DEBUG_VAR(test_num,20);
		wait(1);
	}
}

function on_f1_event() 
{
	beep();
	
	//clear all strings

	str_cpy(test_str,"");
	test_num=0;
	

	

	char this_char = 0;
	is_input_box_on=1;
	
	while(this_char!=13)//wait until press enter
	{
		

		this_char = inchar(defstr);
		if(this_char!=1)  
		{
			//if is numeric
			if(str_stri(this_char,"0")||
			str_stri(this_char,"1")||
			str_stri(this_char,"2")||
			str_stri(this_char,"3")||
			str_stri(this_char,"4")||
			str_stri(this_char,"5")||
			str_stri(this_char,"6")||
			str_stri(this_char,"7")||
			str_stri(this_char,"8")||
			str_stri(this_char,"9"))
			{
				str_cat(test_str,defstr);
				
			}
			else
			{
				//if isn't numeric don't do anything
			}
			
		}
		wait(1);
	}

	//convert string to number
	test_num=str_to_int(test_str);
	
	//turn of the box
	is_input_box_on=0;

	
	//if bigger than 100
	if(test_num>100)
	{
		printf("Error: Value is bigger than 100!");
		
		//try again
		on_f1_event(); 
	}

}




function main()
{

	on_f1_event();
}
void on_esc_event()
{
	sys_exit("");
}