## Need help in calculating percentiles

I am trying to determine how I can use Excel to calculate the 40th and 60th percentiles of 3 different data sources.

Specifically, in one study I know the 25th, 50th, 75th, and 90th percentiles.

In another study, I know the 20th, 50th, 80th, and 90th percentiles.

In the final study, I know the 10th, 25th, 50th, 75th, and 90th percentiles.

I am trying to calculate the 40th and 60th percentiles of the combined sources.

Can anyone tell me if Excel can compute these data points? How? If Excel cannot compute them, does anyone know a software package that can?