At a guess I'd say it's because you're trying to use " inside a string. That would make the string end (thus making you call
/dde mirc command.)
Try this:
Private Sub gfdgfdfdg_Click()
'Create a DDE connection
If Text1.LinkMode = vbNone Then
Text1.LinkTopic = "mIRC|COMMAND" 'Set link topic.
Text1.LinkMode = vbLinkManual ' Set link mode.
End If
Text1.LinkExecute "/dde mirc command " & chr(34) & chr(34) & " /echo -a %test"
End Sub
By the way, I'd recommend sticking to one language, if you keep switching between different languages you won't get anywhere.