CISCO 7690 short keys -> part of a number

Hi!

Is it possible to save only a part of a number, so that I can complete the number after I pressed a soft key?

For example:

SoftKey6: 123456

When I want to call, I press SoftKey6 and 789 to call a specific person.

I tried it, but when I press a soft key I can't append the direct dial because the 7690 dials directly the number.

Are there any settings or tricks?

Thx

KUZB