Hi,
You may want to check out a similar community thread here where a MDX calculation is given: Can I duplicate my work hour formula in Eazy BI
Adjust calculation formula given by Daina for 8 hours instead of 9 and 9-17 instead 9-18 (there are comments in the formula which parameters mean the number of hours and which - working hours)
Best,
Ilze / support@eazybi.com