Check Variable

I am attempting to write a piece of code and I need to determine if a passed variable contains letters. My intVar1 is from a response.form which should be a number, but of course the user could input a string instead of a number in the form. This all works unless I give it something other than a number

Here is my current code:
if intVar1 <> "" Then
intFixVar1 =int(intVar1)
if intFixVar1 < 1 Then
Response.Write "my message"
else
if intFixVar1 > intVar2 Then
Response.Write "my other message"
else
intVar3 = intFixVar1
End if
end if
end if