form validation Greater than not a number

I am trying to validate the value of one text box to the value of another. The text box hold a number and I want it to check if it is greater than the value of another number (this number is dynamic depending on the page loaded)

Code:

---

dim InputError,Reason
InputError=0

If Len(inventory) > Len(allocation) Then
        Reason = "<strong>ERROR:</strong> inventory can not be greater than allocation!!"
        InputError=InputError+1
end if
if InputError = 0 then


rsUpdateEntry.Update

---

As you can see I'm trying to get the inventory value=5 to check if it is greater that the allocation value=4, if it is, return error message.

This is not working, does anyone know how to validate the values of two fields that will who's values will change dependent upon the page loaded?