Why Does This Not Work? And How can I get It to Work? FILTER Command

[tmendoza]

CALCULATE(SUM(Table1[Amount]), FILTER(ALL(Table1[Period], VALUE(Table1[Period]) = Table1[Period] -1)

However, This works:

CALCULATE(SUM(Table1[Amount]), FILTER(ALL(Table1[Period], VALUE(Table1[Period]) = Table1[Period] )

I'm trying to find the Amount of the previous period. Thus, the Table1[Period] -1

I believe the formula is compatible because the formula browser or what ever it is called is not yelling at me telling me the formula does not work (Yellow footer with reasoning why formula doesn't work). I hit the check mark and it accepts the formula, yet produces nothing.