How to build a code library and include it in projects?

How can I build a single code library to include in multiple projects?

I have had a look on Google, but I am spending a surprisingly frustrating amount of time getting nowhere!!!!!!!

In every other language that I've ever written code in, you can do this very simply.

E.g. in PHP, you just do:

PHP Code: 

include_once ("mylibrary.php"); 


I am assuming that I can write VBA code in a file that is not associated with a workbook, then somehow include that file in the projects of multiple workbooks.

I am assuming that you can do this, because to not be able to do that, and to have to copy and paste your functions into every single new project that you wanted to create would be ... insane ... !!!!

For that reason, I'm sure it's dead simple to do, I just haven't figured it out yet.

The google term that you are after is Add-In

Many thanks for your help so far ... I have much more understanding of how to do it now.

I have decided to go down the Add-In route - it seems more intuitive to me (being used to writing code libraries in other languages) and it seems the most portable/deployable solution for my needs.

My efforts so far:

I have created a workbook to contain the library code, here: testlib.xlsm

I have saved it as an XLAM file; Excel chose to save it in the default Add-Ins directory, namely as C:\Users\XmisterIS\AppData\Roaming\Microsoft\AddIns\testlib.xlam

I am following the instructions here: http://www.cpearson.com/excel/createaddin.aspx

But I have come to a stumbling block. The instructions state:

"You can store the XLA file in any folder you want. The default location for add-ins is the folder named by the Application.UserLibraryPath property. The value will depend on your version of Excel and your version of Windows. On my Windows Vista Ultimate machine, that path, in both Excel 2003 and 2007, is

C:\Users\Pearson\AppData\Roaming\Microsoft\AddIns

If you save the XLA file in the Application.UserLibraryPath folder, Excel will automatically add the Add-In to the list of available Add-Ins displayed in the Add-Ins dialog box. If you save the XLA to another folder, you will need to click the Browse button in the Add-Ins dialog and navigate to your XLA file. In either case, you will need to check the box next to your add-in to open and load the Add-In."

The problem is that (a) My add-in doesn't appear in the list of add-ins when I open excel. (b) Application.userLibraryPath does indeed point to where the add-in is saved. (c) I don't know where the "browse button in the add-ins dialog" is, and anyway, if I am reading the instructions correctly, then my add-in should automatically appear in the list of add-ins. But it doesn't. So I am doing something wrong ...

Excellent! I got it, thanks to you guys.

My HelloWorld function is now available for anything that wants to use it.

Easy when you know how!!