使用VBA输入盒进行错误处理的奇怪流程？

Question

我试图理解为什么下面的代码没有给我预期的行为.

我想问用户一个十进制数(双).我有一个错误处理程序,但这个程序的行为方式,当我输入一个单词或数字时,它仍然会抛出错误.当我没有放任何东西(空输入)时它会捕获错误.

当我删除if条件时,它将按预期工作,但我不知道如何捕获空用户输入.

任何想法将不胜感激!

Sub MainTask()

Dim userInput As Double

TryAgain:
    On Error GoTo ErrorHandler
    userInput = InputBox("What is the amount purchased you would like to search for? ($)")
    If Len(userInput) = 0 Then
        Exit Sub
    End If
    MsgBox "You have entered a valid value!"
Exit Sub

ErrorHandler:
MsgBox "Please enter a valid value."
GoTo TryAgain

End Sub

Answer 1

我不喜欢错误处理,因为它将涵盖其他问题:

Sub MainTask()

Dim userInput As Variant
Dim output As Double

Do
    userInput = InputBox("What is the amount purchased you would like to search for? ($)")
    If Len(userInput) = 0 Then Exit Sub
    If Not IsNumeric(userInput) Then MsgBox "Please enter a valid value."        
Loop Until IsNumeric(userInput)

output = userInput
MsgBox "You have entered a valid value! " & output   

End Sub