Say, c:\FitFunc.dll is not a resource-only dll, then you might execute the following LabTalk script to unload it:
dll -rc c:\FitFunc.dll
Not sure if it works in such an old version as 7...
©c¡Ï ¤È¥¹ ©f¨u©c ©c¥ì ¥Î¤³ ©c/ ©¦£¯
©c¨Ê¥Î ¤´¥¨ ¥ó ¨× ¥ó¤á' ¥Ì©¦¥ /¤í ¥Õ©¦©f
¨Ö ¦á ©¦£þ ©` ¥Õ ©¦
©¦