Create two blocks. 1) The block1 whose data you want when you select the right values. 2) The block2 just having “Sorry you have entered a typo. Please select again”
Create the variable with this.
nrow=NumberOfRows(DataProvider(<Year>))Place the blocks one over the other and write hide condition in the appearance tab of the format table window.
For block1 write ==0 and then check hide
For block2 write = > 0 and then check hide.
Now when you run, if you enter right values, then block1 will be displayed. If not, the second block will be displayed with the message you have into it.
But this will give a friendly message after the report execution…
For just suppressing the error messages, you can have a look into other options from here.
Jansi 
(BOB member since 2008-05-12)