how would i code some kind of validation into this peice of code so it only accepts numbers?? maybe case statements// help

Private Sub Command2_Click()
For this = 1 To 18
num = InputBox("Please enter your scores")
nos(this) = num
If nos(this) < 1 Then
MsgBox "Error please enter a valid number > 0"
this = this - 1
End If
Next this
For Counter = 1 To 18
Text1 = Text1 & " | " & nos(Counter)
Next Counter
End Sub

is there any way to take an array back a loop if the dat entered doesnt meet the required format.