I need the following if statement to be true for times when the the text box
Rider5.Text is numbers less than 100 (done), or any text value, or blank. I
can put in the or statements but don't know what function to use.

'When rider number is less than lowest rider number or Any text value
(entered in error)
If Rider5.Text < 100 Then
UnkRow = Sheets("Unknown").Cells(Rows.Count, "A").End(xlUp).Row + 1
Sheets("Unknown").Range("A" & UnkRow) = Rider5.Text
Sheets("Unknown").Range("B" & UnkRow) = Time5.Text

Thanks