Code:
STRING* str_input;
STRING* str_temp;
STRING* str_flush_buffer="#100";
STRING* str_textbox[10];

function fill_textboxs()
{
  int I;
 for(I=0;i<10;i++)
    {
       str_textbox[I]=str_create("");
     }
}

function str_mod()
{
int int_str_len;

str_cpy(str_input,str_flush_buffer); // Clear the input
int_str_len=str_len(str_textbox[0]); // Find current len of textbox
str_cpy(str_temp,str_textbox[0]);    // move textbox into temp/ or use a textbox_dply[array size of textbox]
str_cat(str_temp,str_flush_buffer);  // add the maximun input len of white spaces
str_trunc(str_temp,int_str_len);     // cut textbox len of white spaces off end of temp
str_cpy(str_input,str_temp);         // fill the input text + white_space trunced to max 
inkey(str_input);                    // Edit text
str_cpy(str_textbox[0],str_input);   // replace text in texbox
int_str_len=str_len(str_textbox[0]); // degubbing only
}




Not sure how this works but it's an idea to work from

Mal