Pass Array Variables Between Modules

I am trying to pass a public variable to another module in the same workbook. On Module1 I declare at the top

Public stores
Sub Main()
Dim stores(1 To 100, 1 To 10, 1 To 10)

Reader

...which then calls the procedure Reader in Module2

Sub Reader()
let x=1
let y=1
let z=1
let stores (x,y,z)=activecell.value

I've left out the portions of code that seem irrelevant. When the macro runs, I get a type mismatch error on the "let stores" line. If I move the code from Reader into the procedure Main, it works, so it seems to be an issue with passing the variable. I haven't used multiple modules very often so this is probably a very basic issue.