Unresolved external 'TFormCountSell_Goods:' referenced from D:\LITTLEMALL\

十万火急Unresolved external 'TFormCountSell_Goods::' referenced from D:\LITTLEMALL\
十万火急，现在要解决的问题：
[Linker Error] Unresolved external 'TFormCountSell_Goods::' referenced from D:\LITTLEMALL\MALL.OBJ

Mall是一个工程，FormCountSell_Goods是其中一个窗体

请问 Unresolved external 是什么错误，如何才能尽快解决呢
急救啊

[解决办法]
TFormCountSell_Goods 检查一下这个窗体的构造函数是否正确
[解决办法]
有声明，没定义。