For creating drop dpwn list from another workbook, please do as follows.
1. Open and rename the workbook which contains the source data as “SourceData” or others you like.
2. Select the cell range that contains the data, such as A2:A10. And then click Formular > Define Name. See screenshot:
3. In the popping up New Name dialog box, name the range as SourceList in the Name box, and click the OK button.
4. Press Ctrl + S to save the workbook.
5. Open the another workbook and select the specific worksheet you need to create the drop down list in, and click Formula > Define Name.
6. In the New Name dialog box, you need to:
1). Enter a name in the Name dialog box. In this case, we enter New;
2). Copy and paste =SourceData.xlsx!SourceList to the Refers to box;
3). Click the OK button. See screenshot:
Notes:
1). The SourceData in this formula is the name of the workbook that contains the source data;
2). And the SourceList is the range name you specified in the source data workbook;
3).
If there are spaces or other characters such as -, #... in the name of
the source data workbook, you need to add single quotation marks such as
='Source Data.xlsx'! SourceList.
7. Select the cells for creating drop down list, and click Data > Data Validation.
8. In this Data Validation dialog box, go to the Settings tab, select List in the Allow drop-down list, enter =New in the Source box, and finally click the OK button. See screenshot:
Note: The =New you entered into the Source box is the range name you specified in above step 6.
9. Then a Microsoft Excel prompt box pops up, just click the Yes button.
Now the drop dow list is created with the data in other workbook. See screenshot:
source: http://www.extendoffice.com/documents/excel/2442-excel-drop-down-list-from-another-workbook.html