You mean this ?
;; Set Attribute Value - Lee Mac
;; Sets the value of the first attribute with the given tag found within the block, if present.
;; blk - [vla] VLA Block Reference Object
;; tag - [str] Attribute TagString
;; val - [str] Attribute Value
;; Returns: [str] Attribute value if successful, else nil.
(defun LM:vl-setattributevalue ( blk tag val )
(setq tag (strcase tag))
(vl-some
'(lambda ( att )
(if (= tag (strcase (vla-get-tagstring att)))
(progn (vla-put-textstring att val) val)
)
)
(vlax-invoke blk 'getattributes)
)
)