How to create an Expression Tag in E3?

Linking an Internal Tag's Value property to this expression. This expression can be simple and may contain arithmetical and logical operators involving constants and other Tags.

How can I change the color of an object when moving the mouse pointer over it?

Creating a Digital Link between object's ForegroundColor and MouseOver properties. The MouseOver property has a Boolean type, and assumes a True value when the mouse pointer is over this object and False when the mouse pointer is outside this object's area.

How can I create a multilingual application?

One way is creating an Internal Tag in Viewer for each String and link these Tags to these properties to translate, or use Tags on scripts in case of using the Msgbox method. Then, create a table with all application Strings, where the first column is the name of an Internal Tag created in Viewer, and each subsequent column contains a String corresponding to a language. This table can be created in Access, for example. When opening Viewer and defining a language, load Viewer's Internal Tags with a table of Strings corresponding to the selected language. This can be performed using a Query object on a Screen, as in the next script.

Sub Screen1_OnPreShow(Arg)
  Set rs = Item("Query1").GetADORecordset()
  rs.MoveFirst
  For i = 1 To rs.RecordCount
    Application.Item(rs.Fields("TagName").Value).Value = _
      rs.Fields(Arg).Value
    ' Arg is a parameter passed to the Screen
    ' containing the name of the column
    ' referring to the chosen language
    rs.MoveNext
  Next
End Sub

Another way is creating a Table Link in all properties with translatable content, using the same source for all Links. For each value range of this Link, place a String referring to a different language. The source can be an Internal Tag whose value can be defined when opening Viewer. In case of using the MsgBox method, use the same Tag as a condition to choose which String is used.