T-SQL (SS2K8) :: Using Not Like To Filter Out Non-numeric Values From Varchar Field

I am putting a SELECT statement together where I need to evaluate a results field, to determine how the color indicator will show on a SSRS report. I am running into a problem when I try to filter out any non-numeric values from a varchar field, using a nested CASE statement.

For example, this results field may contain values of '<1', '>=1', '1', '100', '500', '5000', etc. For one type of test, I need a value of 500 or less to be shown as a green indicator in a report, and any value over that would be flagged as a red. Another test might only allow a value of 10 or less before being flagged with a red.

This is why I setup a CASE statement for an IndicatorValue that will pass over to the report to determine the indicator color. Using CASE statements for this is easier to work with, and less taxing on the report server, if done in SQL Server instead of nested SSRS expressions, especially since a variety of tests have different result values that would be flagged as green or red.

I have a separate nested CASE statement that will handle any of the values that contain ">" or "<", so I am using the following to filter those out, and then convert it to an int value, to determine what the indicator value should be. Here is the line of the script that is erring out"

case when (RESULT not like '%<%') or (RESULT not like '%>%') then
CASE WHEN (CONVERT(int, RESULT) between 0 and 500) THEN '2'
ELSE '0'

The message I am getting is: Conversion failed when converting the varchar value '<1' to data type int.

I thought a "not like" statement would not include those values for converting to an int, but that does not seem to be working correctly. I did also try moving the not to show as "not RESULT like", and that did not change the message.

How I can filter out non-numeric values before converting the rest of the varchar field (RESULT) to int, so that it is only converting actual numbers?