Need help with powerpivot if function

Hi all. I'm a pretty new poster, but I've reviewed the site for some time now. I'm having trouble with a function and I didn't find any help reading through other's posts.

I'm trying to come up with a function for a powerpivot measure. I know this formula is wrong, but I can't figure out how to rewrite it in the proper DAX context.

=IF(Table1[Hardware category]) = "Medical hardware", sumx(Table1,[Installations]),sumx(Table1,[Installations])/DISTINCTCOUNT([Professional grade]))

Basically what this formula is doing is calculating the sumx of a column and dividing it by the distinct count of another column. However, I have some data (cells in the hardware category column that contain "Medical hardware" that I don't want to be divided by the distinct count.

By the way, if I make the formula =IF(VALUES(Table1[Hardware category])) . . . the formula works, but it breaks the pivot table b/c it is blank unless only one item is selected in the hardware category.

How do I do this?