Define variable in macro than calling that macro inside another macro

The module is just the location of a procedure / macro. If you want to call a procedure from another module entirely, you need to make the subroutine Public.

If you want to simply call a procedure from with the same module, you only need to use its name or along with the Call function.

Sub Callsub()
Call Myvars
Cells(3,3)=rn
End Sub

or

Sub Callsub()
Myvars
Cells(3,3)=rn
End Sub

And then here's an example of module to module:

Module1:

Public Sub MessageHi()
Msgbox "Hi"
End Sub

Module2:

Sub ShowHi()
Call MessageHi
End Sub

Maybe:

Dim rn As String
Sub Myvars()
    rn = "A"
End Sub

Sub Callsub()
    Call Module1.Myvars
    Cells(3, 3) = rn
End Sub

Glad to help.