No. Depending on the function the option may be there (InStr for example) as an optional parameter, but for just straight comparison, there is no global option.
One little known option that can be handy is if you have a list of strings and you want to see if a string is in that list:
Dim dicList : Set dicList = CreateObject("Scripting.Dictionary")
Dim strTest
dicList.CompareMode = 0 ' Binary ie case sensitive
dicList.Add "FOO", ""
dicList.Add "BAR", ""
dicList.Add "Wombat", ""
strTest = "foo"
WScript.Echo CStr(dicList.Exists(strTest))
Set dicList = CreateObject("Scripting.Dictionary")
dicList.CompareMode = 1 ' Text ie case insensitive
dicList.Add "FOO", ""
dicList.Add "BAR", ""
dicList.Add "Wombat", ""
strTest = "foo"
WScript.Echo CStr(dicList.Exists(strTest))