In the combobox "CargarCarreteras" I already have the items I need to fill the "VIA" bookmark.

In the Module "formulario" I have the code created by you to fill markers, I have called it "Rellenar"(in English it is written "Fill"):

#Public Sub Fill(strMarkerName As String, strValue As String).
'Gorka Cuairan. Function that fills markers
Dim Rng As Range
With ActiveDocument
On Error GoTo lbl_Exit
Set Rng = .Bookmarks(strMarkerName).Range
Rng.Text = strValue
Rng.Bookmarks.Add strMarkerName
End With
lbl_Exit:
Set Rng = Nothing
Exit Sub
End Sub

The idea is that in the Module "termino", I enter the values I need, but I don't know how to do it and I don't know how to pass it to the variable strValue of the previous procedure.

The same for the Modules "denominacion" and "partido".