Creating a calculated column in Matrix

[Crawfom]

I am a newbie to PowerBi and am getting stuck.

I have a Matrix built from source data and want to add a 3rd column which is <<Current period>> divided by <<Last Year>>.

When I build a column in the data table to do this at an individual row level I get 'infinity' and this feeds through to the Matrix table. This is because I do have some zero and blank cells

What I want is (for example) on the mixed row .... sum(33,880,066.38/34715472)

The eroneous output looks like this

Thanks for your help (I suspect it is REALLY easy)

[mickey64 · Accepted solution]

For your reference.

How about a measure below?

Measure = DIVIDE(SUM([Current Period]),SUM([Last Year]))

[Crawfom]

mickey64 - thank you.

I added a new "measure" into the data table using your formula then a new column into the Matrix - which gave me the right answer!  

Everyday is a learning day and you have helped me on this one - thank you!