Calculating Percentages for line items with data selected by slicer

Hi pAAmckelvey,

Based on my test, you can refer to below steps:

1.I have entered some sample data to test for your problem in below picture.

2.Create a new measure to calculate the percentage.

percentage = DIVIDE(SUM(Sheet2[Hours]),CALCULATE(SUM(Sheet2[Hours]),ALLSELECTED(Sheet2[Work Description])))

3.Create a Table visual and add the [Work Description] and the [Hours] field. Create a Slicer visual to add the [percentage] field. And now you can see the result.

You can also download the PBIX file to have a view.

 https://www.dropbox.com/s/7y8x1qrqy3h03qm/Calculating%20Percentages%20for%20line%20items%20with%20data%20selected%20by%20slicer.pbix?dl=0

Regards,

Daniel He