Very Simple ICSP Programmer

[shottootto]

Hi
I am completely new to PIC, so please excuse if this is stupid.
For Stand-alone(not in-circuit) I understand that to transfer a program I need approx 12V on VPP and this has to be connected after 5V to VDD.
Can I use an external power supply for both voltages and make the VPP 12V switched in by the VDD 5v via a transistor, can it work or is VPP switched during transfer?

So I will then only have these between PC and PIC

GND (5) --------------------VSS

DTR (4) -------[4.7k]------DATA
- |
CTS (8) -----------------

RTS (7) -------[4.7k]------CLK

If it can work, then surely it will solve the laptop and USB-232 adapter problems.
Ps. I know I can buy a programmer, but I want to build one. This is why I ask.

Will appreciate your help.