Finalmente, tengo una solución. Enormes gracias a Monomeeth por la versión VBA que me puso en el camino correcto. (Y hacer que esto también sea posible en Windows)

Funciona de forma similar a la versión de Monomeeth. Tiene un rango considerado por razones de rendimiento. Establézcalo cambiando esta línea en consecuencia:

set range_considered to range "A1:Z100" of active sheet

Aquí está:

-- use "intersect" to test whether the considered area overlaps with the selected area
-- use union to append non-selected cells to a new range

tell application "Microsoft Excel"
    set screen updating to false -- optimize performance
    --tell active sheet of active workbook
    set range_considered to range "A1:Z100" of active sheet
    set range_selected to selection
    set range_new_selection to "Nothing"

    -- setup ref vars for selection
    tell selection to set {range_selected_row_index, range_selected_column_index, range_selected_row_count, range_selected_column_count} to {get first row index of selection, get first column index of selection, get count rows of selection, get count columns of selection}
    -- setup ref vars for considered
    tell selection to set {range_considered_row_index, range_considered_column_index, range_considered_row_count, range_considered_column_count} to {get first row index of range_considered, get first column index of range_considered, get count rows of range_considered, get count columns of range_considered}

    -- go column by column and iterate each row in each column
    repeat with considered_col_step from range_considered_column_index to range_considered_column_count
        repeat with considered_row_step from range_considered_row_index to range_considered_row_count
            set range_this_cell to range (get address row considered_row_step of column considered_col_step of active sheet) of active sheet
            log range_selected
            try
                set range_test to intersect range1 range_this_cell range2 range_selected -- test for intersection with selected
                (*use try to detect error. Will fail if cell is within selection*)
                log "TRUE Intersected"
            on error
                (*Create or append to range_new_selection*)
                log "FALSE intersected"
                if range_new_selection is "Nothing" then
                    set range_new_selection to range_this_cell
                else
                    set range_new_selection to union range1 range_new_selection range2 range_this_cell
                end if
            end try
        end repeat
    end repeat
    try
        select range_new_selection
    on error
        log "Could not select new range."
    end try
    set screen updating to true -- optimize performance
end tell