VBA Function for Correlation matrices WITHOUT invoking any worksheetFunction

Question

i'm looking for a way to calculate a correlation matrix of a bunch ob observations. My trials are so far this:

Function VarCovar(Rng As range) As Variant
Dim i As Integer
Dim j As Integer
Dim numcols As Integer

numcols = Rng.Columns.Count
Dim matrix() As Double
ReDim matrix(numcols - 1, numcols - 1)
For i = 1 To numcols
    For j = 1 To numcols
        matrix(i - 1, j - 1) = Application.WorksheetFunction.Covar(Rng.Columns(i), Rng.Columns(j))
    Next j
Next i

VarCovar = matrix

End Function

However, i'd like to aviod this Application.WorksheetFunction.Covar part and write it explicitly in the code. Would anyone mind to help me? Thanks a lot Best regards Thomas