Ya probaste de esta manera:
Código:
comando = New OleDb.OleDbCommand("select sum(Total) from Llamadas_Local where Fecha Between 01/" & DateSelectedByIndex & "/2007 and 30/" & DateSelectedByIndex & "/2007", Conexion)
o talves con:
Código:
comando = New OleDb.OleDbCommand("select sum(Total) from Llamadas_Local where Fecha Between 01/'" & DateSelectedByIndex & "'/2007 and 30/'" & DateSelectedByIndex & "'/2007", Conexion)
Espero te sirva.....