VLISP Example Modification Not Working

Trying to get to grips with VLISP by modifying example code to suit my needs, I have hit a brick wall with this one:

(defun c:Test (/ acadObj doc ss oML modelSpace sBlock MLval)

(vl-load-com)

;Modified VLISP example from Autodesk ActiveX Reference Guide
;Change MLeader content type from BLOCK to MTEXT assigning attribute value to text string

   (setq acadObj (vlax-get-acad-object))
   (setq doc (vla-get-ActiveDocument acadObj))
   (setq modelSpace (vla-get-ModelSpace doc))
   
   (setq ss (ssget "_:L" '((0 . "MULTILEADER"))))
 
   (repeat (setq i (sslength ss))
   (setq oML (vlax-ename->vla-object (ssname ss (setq i (1- i)))))
 
   (setq sBlock (vla-get-ContentBlockName oML))

   (vlax-for o (vla-Item (vla-get-Blocks doc) sBlock)
               (setq MLval (vla-GetBlockAttributeValue oML (vla-get-ObjectID o))) ;Read MLeader Block Attribute Value
               (vla-put-contenttype oML acMTextContent)    ;Change MLeader Content Type to MTEXT
               (vla-put-textstring oML MLval)                 ;Assign Attribute Value to MTEXT text string
   )
 )
   (vla-Update acadObj)
)

Can anybody help?

Cheers,

Maybe a typo vla-Get-BlockAttributeValue