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Code:
Private Sub Text1_GotFocus()
Text1.SelStart = 0
Text1.SelLength = Len(Text1.Text)
End Sub
Private Sub Text1_LostFocus()
Text1.SelLength = 0
End Sub
As far as Enter key goes, I'll leave that to you. You'll want to use its KeyPress event or KeyDown event.
In either case, check the textbox's .SelLength and if > 0 then stuff is highlighted.
Notes:
1. When a textbox loses focus, you can't see any selection unless the HideSelection property is set to False.
2. When text is highlighted and you press a key under normal conditions, what was highlighted is lost and replaced with that key stroke. Ensure you address this when handling the Enter key by setting to zero, the KeyAscii or KeyCode parameter (depending on which event you'll trap the enter key in). Enter key doesn't erase text in single-line textbox mode.