帮忙看一下这答题，前面要求的代码已经给出了，剩下后面三个问题

Private Sub Text1_Change()'6ifText1.Text="" orText2.Text="" orText3.Text="" thencommand1.enabled=falseelsecommand1.enabled=trueend if'7ifVal(Text1.Text)<0 orVal(Text1.Text)>100 thenmsgbox "成绩输入有误，应在0-100之间"Text1.Text=""Text1.setfocusend if'8Label4.Caption=""end subPrivate Sub Text2_Change()'6ifText1.Text="" orText2.Text="" orText3.Text="" thencommand1.enabled=falseelsecommand1.enabled=trueend if'7ifVal(Text2.Text)<0 orVal(Text2.Text)>100 thenmsgbox "成绩输入有误，应在0-100之间"Text2.Text=""Text2.setfocusend if'8Label4.Caption=""end subPrivate Sub Text3_Change()'6ifText1.Text="" orText2.Text="" orText3.Text="" thencommand1.enabled=falseelsecommand1.enabled=trueend if'7ifVal(Text3.Text)<0 orVal(Text3.Text)>100 thenmsgbox "成绩输入有误，应在0-100之间"Text3.Text=""Text3.setfocusend if'8Label4.Caption=""end sub