You can add all the data you want to a single CCK field, but you need a CCK type that supports this.
With CCK you can specify, how the data store should be (field_settings), how the form for inputting should be (widget) and how the field should be renderen (formatters).
You're not quite clear on how you want things, but the easiest thing to do, would be to create a have a single input/storage, and use a custom formatter to display the single value as two, based on some regex or similar.
You could also make your widget, that would create a custom form for the field and how the data should be stored. If multiple values is setup for the field, you could use
delta to separate the values. This requires more in depth knowledge of the inner workings of CCK, but would give you better data control.
The documentation on doing all of this is very limited, but looking at other modules will give you an idea on how to do it.