Sample code for 30+ languages & platforms
Visual Basic 6.0

Duplicate openssl pkcs12 –export –in certfile.cer –inkey certfile.key –out certfile.pfx

See more OpenSSL Examples

How to create a PKCS12 (.p12 or .pfx) from a certificate file and private key file: Demonstrates how to duplicate this OpenSSL command:
Duplicate openssl pkcs12 –export –in certfile.cer –inkey certfile.key –out certfile.pfx

Chilkat Visual Basic 6.0 Downloads

Visual Basic 6.0
Dim success As Long
success = 0

' This example assumes the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

Dim pkey As New PrivateKey

' Load the private key from the file.
success = pkey.LoadAnyFormatFile("certFile.key","")
If (success <> 1) Then
    Debug.Print pkey.LastErrorText
    Exit Sub
End If

Dim cert As New ChilkatCert
' The LoadFromFile method auto-recognizes the format...
success = cert.LoadFromFile("certfile.cer")
If (success <> 1) Then
    Debug.Print cert.LastErrorText
    Exit Sub
End If

' We'll need a cert chain object to create the PKCS12, so get it
' from the cert.  
Dim certChain As ChilkatCertChain
Set certChain = cert.GetCertChain()
If (Not cert.LastMethodSuccess) Then
    Debug.Print cert.LastErrorText
    Exit Sub
End If

' Create the PFX object, add the cert and private key, and write to a .pfx file.
Dim pfx As New ChilkatPfx

' The cert(s) are automatically added in the call to AddPrivateKey
success = pfx.AddPrivateKey(pkey,certChain)
If (success <> 1) Then
    Debug.Print pfx.LastErrorText
    Exit Sub
End If

' Write the .pfx to a file.
Dim password As String
password = "myPassword"
success = pfx.ToFile(password,"certfile.pfx")
If (success <> 1) Then
    Debug.Print pfx.LastErrorText
    Exit Sub
End If

Debug.Print "Success."