Calculating Averages

[ozirambler]

I recently started in shares and I am now trying to prepare spreadsheets for taxation purposes

My first question is how to work out share average costs

I bought 4878 shares at a price of $8.146525
I bought 2800 shares at a price of $19.2
now I have 7678 shares at a price of $12.192(as provided by share trading platform)

How do I work this out on an excel sheet?

[FDibbins]

1. start with 3 columns (QTY/Price/Cost)
2. put each transaction detail into each column (Cost = QTY*Price), 1 row per purchase
3. Sum QTY and Cost
4. AVG cost = tot QTY/TOT Cost