vba programming for visio

Currently, I am working for IVR(Interactive Voice Response) System. To add the service in the IVR, I have to make the flow in the visio which have pre-defined shape provided by the seller of IVR SYstem. The shape is programmed in VBA. I decided to learn VBA for modification in the pre-defined shape. While searching in google, It shows the only results for excel VBA programming. Is it same for visio also. Please help me to get the source for the learning the VBA programming for MS VISIO. So, that I can add new shape for customizing the service

As Tim points out there lots of good stuff on the Visio VBA search, but I'll add a few links as well.

The language (VBA) is just the same as what you're finding for Excel. The difference is the object model. Excel deals with Workbooks, Worksheets and Ranges, while Visio deals with Documents, Pages and Shapes. To be useful at the automation side you also need to understand the ShapeSheet as you be writing code that talks to this 'properties window' alot.

I wrote a 'Just for starters' post a while ago for people new to Visio development, but other good resources are as follows:

Microsoft Visio 2010 SDK (including VBA code library)
Developing Microsoft Visio Solutions (DVS) - Chapter 14 onwards
Visio Insights - Visio team blog (programming category)
Visio.mvps.org/VBA
Visio Guy (code category)
David Parker (no code category but packed full of code examples)

...and that's not it. Any of the above blogs, mine included, have lists of other blogs and resources, but this should do you for the time being.

[Update 27th June 2016 - I'll add another resource which may be helpful for developers wanting to interact with Visio and that's a two-part video course I recently put together - 'Visio, a flyby for developers']