Trouble adding item to a list with a lookup value

I am adding a new item to a list in SharePoint 2007. One of the columns is a lookup into anoth开发者_C百科er list. Here is the code:

li["LOOKUP"] = new SPFieldLookupValue(1,VALUE);

The entry in the list isn't correct and is always using the first value in the other list. When I look at the value of li["LOOKUP"] in the debugger all I get is "1".

VALUE is in the other list and it is the first column.

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When adding items to a list only the id of the element from the list being looked up needs to be provided. It was always adding the first element because I always passed in "1". The following code looks up the value and then gets its id and passed this to the field:

SPListItemCollection lookup = LIST.GetItems(qry);
li["LOOKUP"] = lookup[0][SPBuiltInFieldId.ID].ToString();