It's for named parameters. For example:
<br />Sub ShowMsg(ByVal a as String, ByVal b as String, ByVal c as String)<br /> MsgBox(a & b & c)<br />End Sub<br /><br />Sub Main()<br /> 'Notice how a, b, and c are out of order.<br /> ShowMsg(c := "!", b := " World", a := "Hello")<br />End Sub<br />