cert.vbs

Sub EnviarComCertificadoCliente()

    Dim http As Object
    Dim url As String
    Dim certSubject As String
    Dim json As String

    url = "https://sua-api.com/endpoint"
    certSubject = "CN=Nome do seu certificado"

    Set http = CreateObject("WinHttp.WinHttpRequest.5.1")

    http.Open "POST", url, False

    ' Configura o certificado cliente pelo subject da store do usuário
    ' O parâmetro pode ser:
    ' "CURRENT_USER\MY\<subject>" ou "LOCAL_MACHINE\MY\<subject>"
    ' Exemplo:
    http.SetClientCertificate "CURRENT_USER\MY\" & certSubject

    http.SetRequestHeader "Content-Type", "application/json"

    json = "{""chave"":""valor""}"

    http.Send json

    MsgBox "Status: " & http.Status & vbCrLf & "Resposta: " & http.ResponseText

End Sub