KBC - Valuing a company is not a fantasy.
Use the data you have for that company. Compare similar companies. Get a read on the current market conditions with buyouts with similar companies, assign some probabilities to the data you have and give yourself a value.
A financing does not give you a value, it gives you a price. When a company needs money the price of a financing will be lower than it would be if a financing was done when a company didn't need the money.
I have been doing this with companies that I hear about for the last 25 years or so. For the ones that survive the accuracy has been surprising.
I do understand that the risk in these small companies is beyond what most people are willing to take on and biotech is at the pinnacle of the risk scale. Many companies don't survive but when they do and get bought out it can be awesome.
tada