Buscas algo hecho o lo quieres implementar tu ?
Aqui te copio un repositorio para convertir:
Microsoft Excel formula to convert ISO 8601 date with milliseconds resolution to time stamp · GitHub
Formula
This will convert an ISO 8601 date such as: 2018-03-19T10:18:08.137747874Z
to a timestamp with milliseconds resolution: 1521454688137,00
Please note that the decimal part (,00) can be stripped away, milliseconds are the last three digits.
Código VB:
=(((DATEVALUE(LEFT(A1;10))+TIMEVALUE(MID(A1;12;8)))-DATE(1970;1;1))*86400000)+VALUE(MID(A1;FIND(".";A1)+1;3))