I have an Basic MSI Project in Installshield 12. There are 2 features (call them A and

If feature A, and .NET framework not present or less than v2 then install .NET Framework 2.0 before installation.
If feature B, and .NET framework not present or less than v1.1 then install .NET Framework before installation.
I have looked at the prerequisites option (and the release wizard within Installshield) which appears to have similar behaviour. This works before the installation is started, and so can not be conditional on the features selected for installation.
My question is, is there a simple way to do this, without resorting to custom actions installing the .NET framework myself? and if so, what would that be?
Many Thanks
Joe