假定有英文字的文本框是Text1,空的文本框是Text2:
Private Sub Text2_KeyPress(KeyAscii As Integer)
If KeyAscii <> Asc(Mid(Text1.Text, Len(Text2.Text) + 1, 1)) Then KeyAscii = 0
End Sub
Dim n As Integer
Private Sub Text2_KeyPress(KeyAscii As Integer)
n = Len(Text2.Text)
If n > Len(Text1.Text) Then Exit Sub
If Mid(Text1.Text, n + 1, 1) <> Chr(KeyAscii) Then KeyAscii = 0
End Sub