IsNumber not working

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[VBA]

For Each x In Range("B:B")
If x.Row > LastCell Then: Exit For
If IsEmpty(x.Value) Then: x.Value = "30"
If IsNumber(x.Value) Then
Select Case (x.Value)
Case 0 To 20: TotalPastDue = TotalPastDue + Range("L" & x.Row) _
- Range("C" & x.Row) - Range("D" & x.Row)
Case 20 To 30: TotalPastDue = TotalPastDue + Range("L" & x.Row) _
- Range("C" & x.Row) - Range("D" & x.Row) - Range("E" & x.Row)
Case 30 To 45: TotalPastDue = TotalPastDue + Range("L" & x.Row) _
- Range("C" & x.Row) - Range("D" & x.Row) - Range("E" & x.Row) - Range("F" & x.Row) _
- Range("G" & x.Row)
Case 45 To 120: TotalPastDue = TotalPastDue + Range("L" & x.Row)
End Select
Next x
[/VBA]

For some reason IsNumber brings up an error message saying "Sub or Function not defined.". What am i doing wrong?

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If statement was causing an error, please delete this thread.
Thanks.

[mdmackillop]

If you use Option Explicit and compile your code before use, any such errors will be revealed.

[Bob Phillips]

IsNumber throws a runtime error with or without Option Explicit, so there was enough info there.

[mdmackillop]

He won't as far as any IsNumber runtime error with the If ... Next code as written.

[mikerickson]

ISNUMBER is a spreadsheet function.
IsNumeric is a VB function.

[next]

i thought that "Option Explicit" just forces you to declare all your vars, how will it reveal errors like this one?

IsNumeric is a VB function.

VB is so much more complicated than the first language that i learned, i'm going to be making those rookie mistakes for a looooooong time.

[mdmackillop]

i thought that "Option Explicit" just forces you to declare all your vars, how will it reveal errors like this one?

Why not give it a try?

[Bob Phillips]

He won't as far as any IsNumber runtime error with the If ... Next code as written.

I did.