Hi Jmgelba,
I think you might have a small confusion going on? VPP is part of MCLR/ RA5 not RA4. MCLR typically has a 4.7k resistor to 5.0v. As for voltages other than 5.0v such as your 15 to 42v I'd probably use a 5.0v voltage regulator IC or an optical isolator to ensure the VPP does not see anything higher than 5.0v. Best, Ed