Correlation formula directly from correlation matrix

Hi there,

I am looking for a simpler way to calculate the correlation between a number of portfolios of assets.

Currently, my method involves translating a correlation matrix into a variance-covariance matrix and calculating covariance using the matrix and the asset weights of each portfolio (using MMULT). Once the covariance is found between each set of portfolios, the numbers are converted into correlations by dividing by the product of each portfolio's standard deviation.

However, this method involves too many steps for my further calculations, and hence I am looking for a simpler solution. Considering I am able to calculate the correlation using a variance-covariance matrix, I believe I should be able to do so directly from the correlation table as well, since the variance-covariance matrix is a product of the correlation table.

I have enclosed a workbook with existing formulas and a specification of which cells I need the formula for. Any help is greatly appreciated.

Thank you!