AutoCAD Visual LISP / AutoLISP :: How To Modify Line Inside A Block

I have a simple block with 2 attribute and 1 line inside it.

something like this:

Attribute1

──────

Attribute2

I want to modify length of line due to width of thoes attributs. length of line is equal to maximum(width attribute1 and width attribute2).

dxf code for start point of a line is 10 and end point for a line entity is 11.The question is: how can I modify the length of line automatically via maximum width of these attributes?

for getting width of a text:

(defun GetWidth ( en ) ((lambda ( lst ) (- (caadr lst) (caar lst))) (textbox en)))
sample:

A1
──────                    
Attribute2

Attribute1
──────           
A2