Wondering if anyone could help me with these functions

When I use the sumif functions and offset functions on one workbook linking
to another workbook it normally works and would give me a value. However
after I saved the workbooks and closed them down and reopen the one that
contains the functions the formulas will give me #VALUE rather than a numeric
result until I open the workbook where the sumif data is linking to

How can I overcome this problem?

Please help

Thanks

Vivi