Surbtaction value (A-B)=C

Hi,

I am searching LISP for Selecting text "A" value and Text "B" value and click on "C" text, then Text "C" automatically should be update as (A-B) as this formula.

for Ex. Text A is "17.010" and Text B is "14.668" if you Select text "A" and Select text "B" and the Select "C" value is automatically updated as "2.342"

It means (A-B)= C (17.010-14.668)= 2.342

Value should be re requere up to 3 desimals.

Is this possible

Thanks

This may help you with it .

If you mess clicking on a text it will return from the beginning ( read the command line while invoking the routine)

(defun c:sub (/ ss1 ss2 ss3 st1 st2 st3 e)
; Tharwat 20.01.2011
(while
  (not (and (setq ss1
           (car (entsel "\n Select first text to subtract from :")))
                (setq ss2
           (car (entsel "\n Select second text :")))
                (setq ss3
           (car (entsel "\n Select text to insert the result:")))
        ))
  )
     (progn
       (setq st1
          (cdr (assoc 1 (entget ss1))))
       (setq st2
          (cdr (assoc 1 (entget ss2))))
       (setq st3
          (cdr (assoc 1 (setq e (entget ss3)))))
         (entupd (cdr
           (assoc -1
                  (entmod (subst
                    (cons 1 (rtos (- (distof st1) (distof st2)) 2 3))
                    (assoc 1 e)
                    e)
                      )
                  )
           )
             )
       )
  (princ)
  )
         

One comment, the OP requested for a double with 3 decimals as a result, so you may want to use DISTOF instead of ATOI in your code; this function will allow you also to validate the content of the string. The same for ITOA vs. RTOS. Thank you.

Regards,

Mircea

That's right Mircea .

Thank you , Codes updated .

Regards,

Tharwat