When using xls format and there are formulas referred to other sheets, reorder sheet's position causes these formulas's reference has been change.
It should not be modified and xlsx format won't get this issue.

reproduce steps:

1. load attached xls file
   • there are 5 sheets and every sheet has formulas referred to other four sheets
2. move sheet "Sheet2" to right
   • the order will be "Sheet1" "Sheet3" "Sheet2" "Sheet4" "Sheet5"
3. switch to "Sheet3", "Sheet4" and "Sheet5", some of their formulas has been changed
   • e.g Sheet3 D1 has been change to "=Sheet3!D1", origin is "=Sheet4!D1"