Drawing a Flow Chart / Schematic / (tree diagram?)

I'm trying to write some code that will draw a schematic diagram from
a list of nodes and connections.

Eg.

Nodes:

Fred
Charlie
Alice
Erbert

Connectors:

Fred to Alice
Charlie to Alice
Alice to Erbert

...........and then I want Excel to be able to 'draw' the diagram.

I've started writing some logic which looks at each node, counts the
number of connections, etc, but I wondered if any of you guys had done
this sort of thing already (so I may "stand on the shoulders of
giants", etc.).

TIA

Dransfield