The following rule should do the trick:
<rule name="teste_seo" stopProcessing="true">
<match url="^script.asp" />
<action type="Rewrite" url="/teste_seo/script.asp" />
</rule>
Then just link to the www.mysite.com/script.asp
Edited after comment from OP:
If so you can use the following rule as long as you have a copy of the script files in the root of your document:
<rule name="teste_seo" stopProcessing="true">
<match url="^teste_seo/([^\.]+\.asp)" />
<action type="Redirect" url="/{R:1}" />
</rule>
And if you need all script files to point to the same one you can use:
<rule name="teste_seo" stopProcessing="true">
<match url="^teste_seo/([^\.]+\.asp)" />
<action type="Redirect" url="/script.asp" />
</rule>
Edited again after clarification:
These 2 rules should then be the fix you need:
<rule name="teste_seo_redirect" stopProcessing="true">
<match url="^teste_seo/([^\.]+\.asp)" />
<action type="Redirect" url="/{R:1}" />
</rule>
<rule name="teste_seo_rewrite" stopProcessing="true">
<match url="^([^\.]+\.asp)" />
<action type="Rewrite" url="/teste_seo/{R:1}" />
</rule>