What does this error mean?

Here's my code:

Sub EnterPerClientFee()
Dim MyString As String
MyString = Application.InputBox("Enter anticipated per-client fee")
Worksheets("Analysis").Range("b20") = MyString
If Worksheets("Analysis").Range("J17") = "TRUE" Then
Exit Sub
Else
MyString = Application.InputsBox("Error. Re-enter anticipated
per client fee")
End If
Worksheets("Analysis").Range("B20") = MyString
End Sub

J17 is a data validation check to make sure that the value entered in B20
matches a value in range B3:B13: =ISNUMBER(MATCH(B20,B3:B13,0))

Basically, I want Excel to check if J17 resolves to TRUE, and, if so, leave
the value in B20, else prompt for a value that matches a value in B3:B13.
What am I doing wrong here?

Thanks,

Dave
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