=NORMINV((K^(RAND())-1)/(K-1), M, S) 

To create right-skewed data, set K > 1 (e.g. let K = 1000)
To create left-skewed data, 0 < K < 1 (e.g. let K = 0.001)

The function will fail (due to a divide-by-zero error) if K = 1

Note that the mean of the distribution will no longer match the value M.