Report Builder query

Hi All,

This may not be in the right area, however here goes;

I have a report that has a number of requirements based on the outcome of another data set, this would if in excel be quite simple, but in report builder it's another matter. I have tried the following, but nothing.

=IF(fields!first date injected field="Y", fields!field with the data you want.Value),(fields!the field you want if the data isn't there.Value))

Please help.