Thanks Andrea
Finally i use the character as a number and use word method to write the equation.
(defun word_inserta_ecuacion_lista (lista)
(mswm-Collapse *range* mswc-wdCollapseend)
(setq sel (vlax-get-property (vlax-get-property *range* "Application") "Selection"))
(mswm-select *range*)
(foreach a (split-list 2 lista)
(mswm-Collapse sel mswc-wdCollapseend)
(mswm-TypeText sel (car a))
(mswm-Collapse sel mswc-wdCollapseend)
(if (cadr a) (mswm-InsertSymbol sel (cadr a) "Cambria Math" :vlax-true)))
(mswp-put-end *range* (mswp-Get-Start sel))
(setq omaths (mswm-Add (mswp-get-OMaths *range*) *range*))
(mswm-BuildUp (mswm-item (mswp-get-OMaths omaths) 1))
)
And use the equation as a list with text and integer (special character)
(word_inserta_ecuacion_lista (list "P_MAX=" 8730 "(3) U I cos(" 966 ")="8730 "(3) 20 kV 50 0A 0,95=16,4 MW"))
8730 is the code of sqrt
966 ins the unicode value of fhi greek
And in word appears the equation good.