Thanks, i understand that my question was not formulated clearly enough. I want to "jump" from field to field in a certain predefined order. For example from a3 to c5 by (for example) the tab key..so a kind of route through the excelsheet.
Other than writing a macro (and even that may not work), the only way I think you could accomplish that is by using "Protection" to protect against change any of the cells that are NOT to be used for input. Leave unprotected the cells that are to be used. Then, if my memory serves me from having seen that done, the cursor will automatically move from valid input cell to valid input cell.