Pairs scoring

I've completed a pairs game in VB (like on Nokia phones, select a block then another to reveal a pair) but I don't feel the scoring is fair enough. I've tried making it so that playing larger boards rewards better but sometimes it's just completely ridiculous.

Please could someone have a look at the code below and advise on a better way of scoring a pairs game. All help appreciated.

Cheers, adehh.

VB Code:

Public Sub CalcScore()
  Dim fScore As Single, lRealsize As Long
  Dim fReward As Single, fClicks As Single, fTime As Single
  lRealsize = m_CurrGame.lSize + 1
  
  fReward = lRealsize * Sqr(lRealsize)
  fClicks = m_CurrGame.lClicks / Sqr(lRealsize)
  fTime = m_CurrGame.lTime / (Sqr(lRealsize) / 2)
  
  fScore = (fReward - fClicks) - fTime
 
  m_CurrGame.fScore = fScore
End Sub