Can I call another application on button in form? And how can I do it?

Goran,

What are you trying to do with the other application? Are you speaking from an Appian application context and want to navigate to that application?

Alternatively, you may be trying to initiate a process associated with another application in Appian. If this is the case, then perhaps you can set some logic in your model to conditionally start a particular sub-process related to this application.