A form's module is a Class Module and procedures in a class
module are methods of the class. From that generalization,
the syntax would be:
Function:
xx = Forms!otherform.procedurename(arglist)
Sub:
Call Forms!otherform.procedurename(arglist)
or
Forms!otherform.procedurename arglist
Note that otherform must be open before it becomes a member
of the Forms collection.
If otherform is not open, you can use the syntax
Form_otherform.procedurename, but that is not the same thing
in cases where the procedure relies on data within the form
or its module.