KISS and untested...

LOCAL loGrid, lcCurs, lcFld, lnIndex
loGrid = SFT.pageframe1.page1.cont1.grid1  && Replace "pageframe1", "page1", "cont1", and "grid" with the actual names of the controls
lcCurs = "fi"
lcFld = "ref"

IF lower(loGrid.RecordSource)==m.lcCurs and USED(m.lcCurs) && and type() plus hoist comparison outside ?
    * Find the column index by ControlSource
    FOR lnIndex = 1 TO loGrid.ColumnCount
         if lower(loGrid.Columns(lnIndex).ControlSource) == m.lcCurs + "." + m.lcFld
            * macro compile done once, oftem faster on recordset cmds
             update &lcCurs SET &lcFld = "Novaref" where empty(&lcFld)
             * Refresh the grid to reflect the changes
             loGrid.Refresh()
             EXIT  && Exit the loop once "REF" column is found
        ENDIF
    ENDFOR
    if  m.lnIndex > loGrid.ColumnCount
         ? "Column 'FI.REF' not found in the grid."
    endif
ELSE
    ? "Invalid or empty cursor name in the grid's RecordSource."
ENDIF

READ EVENTS

>Hi,
>
>I have this code to replace value on specific column in my grid, but sometimes nothing happen.
>

>LOCAL loForm, loGrid, lcCursorName, lnRow, lcControlSource, lcNewValue, lcReplaceCmd
>
>loForm = SFT  && Get a reference to the active form (form with focus)
>loGrid = loForm.pageframe1.page1.cont1.grid1  && Replace "pageframe1", "page1", "cont1", and "grid" with the actual names of the controls
>
>* Get the Cursor/Table name from the Grid's RecordSource property
>lcCursorName = loGrid.RecordSource
>
>IF USED(lcCursorName) AND !EMPTY(lcCursorName) AND TYPE("lcCursorName") = "C"
>    * Find the column index by ControlSource
>    lnCol = 0
>    FOR lnIndex = 1 TO loGrid.ColumnCount
>        lcControlSource = loGrid.Columns(lnIndex).ControlSource
>        IF lcControlSource = "FI.REF"
>            lnCol = lnIndex
>            EXIT  && Exit the loop once "REF" column is found
>        ENDIF
>    ENDFOR
>
>    IF lnCol > 0
>        * Loop through the rows and modify the data in the underlying cursor
>        FOR lnRow = 1 TO _TALLY
>            IF VARTYPE(EVAL(lcControlSource)) = "C"  && Check if the field is a string (character)
>                lcNewValue = "Novaref"  && Replace with your desired new value
>                lcReplaceCmd = 'REPLACE ' + lcControlSource + ' IN (lcCursorName) WITH (lcNewValue) FOR RECNO() = lnRow AND EMPTY(EVAL("' + lcControlSource + '"))'
>                &lcReplaceCmd  && Execute the REPLACE command
>            ENDIF
>        ENDFOR
>    ELSE
>        ? "Column 'REF' not found in the grid."
>    ENDIF
>ELSE
>    ? "Invalid or empty cursor name in the grid's RecordSource."
>ENDIF
>
>* Refresh the grid to reflect the changes
>loGrid.Refresh()
>
>READ EVENTS
>

>
>someone could help me!
>Thanks
>Luis