Heater cable clips

I am trying to install the cable clips on my cuda heater box, and having no luck except entertaining the idea of burning the car. They are new clips and as much as I try to hold the cable and the doors in the right position with one hand and at the same time trying to put the clip on with my arm through the glove box they won't engage. I have tried to use needle nose pliers. Is there a special tool, or technique to get them on before starting a search for the matches?
Monaro.