Adding Misc Charge Items to Sales Order are not being added in BOI

SOLVED

I am currently trying to add in a misc charge item to a sales order using BOI. 

soORDER.oLines.nSetValue("ItemCode$", "/SALESTAX")
soORDER.oLines.nSetValue("ExtensionAmt", 10.00)
soORDER.oLines.sLastErrorMsg #No error message. 
soORDER.oLines.nWrite()
soORDER.oLines.sLastErrorMsg #No error message. 

Above is the code where I am adding the misc charge item but I get no error messages and also the item never appears in the sales order. 

Any help would be greatly appreciate. 

Thank you.