format函數的運用及迴圈~~~(編號:7232)

我用format來定義~~月(1-12)和日(1-31)~~但輸入數字不諭入多少都不會出錯~~不知是不是我語法用錯了~還是~~
還有就是在判斷時我用if then不過會出錯~~我的程式如下~~可否幫我看看是否那出錯了~~tks~~各位麻煩囉~~幫幫我囉~~~
Format (txt_month = " m")
Format (txt_day = "d")
If txt_month = 1 And txt_day >= 19 Then
a = "魔羯座"
If txt_month = 1 And txt_day < 19 Then
a = "水瓶座"
If txt_month = 2 And txt_day >= 20 Then
a = "水瓶座"
If txt_month = 2 And txt_day < 20 Then
a = "雙魚座"
End If
End If
End If
End If
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