Apparently you can also use the Run method as well (not tested by me):

Syntax 1: Runs a macro or calls a function. This can be used to run a macro
written in Visual Basic or the Microsoft Excel 4.0 macro language, or to run
a function in a DLL or XLL.
Syntax 2: Runs the Microsoft Excel 4.0 macro at this location. The range
must be on a macro sheet.

Syntax 1

expression.Run(Macro, Arg1, Arg2, ...)

Syntax 2

expression.Run(Arg1, Arg2, ...)

expression Optional for Application, required for Range. An expression
that returns the application that contains the macro, or a range on a macro
sheet that contains a Microsoft Excel 4.0 macro.

Macro Required Variant for Syntax 1 (not used with Syntax 2). The macro to
run. This can be either a string with the macro name, a Range object
indicating where the function is, or a register ID for a registered DLL
(XLL) function. If a string is used, the string will be evaluated in the
context of the active sheet.

Arg1, Arg2, ... Optional Variant. The arguments that should be passed to
the function.

Remarks

You cannot use named arguments with this method. Arguments must be passed by
position.

The Run method returns whatever the called macro returns. Objects passed as
arguments to the macro are converted to values (by applying the Value
property to the object). This means that you cannot pass objects to macros
by using the Run method.


Run Method Example

This example shows how to call the function macro My_Func_Sum, which is
defined on the macro sheet Mycustom.xlm (the macro sheet must be open). The
function takes two numeric arguments (1 and 5, in this example).

mySum = Application.Run("MYCUSTOM.XLM!My_Func_Sum", 1, 5)
MsgBox "Macro result: " & mySum