is it possible to default another field which has lov

I have a requirement to choose project entry method based from LOV and default value to be picked from Project Type of the selected Project number.

Created the following.

1) Custom Integrator

2) Project Number, Budget Type, Budget Entry Method, Resource List, Resource Alias

3) Lov for Project Number, Budget Type, Budget Entry Method, resource List and Resource Alias.

Challenge i'm facing now is Defaulting Budget Entry Method based on the Project Type setup on the Selected Project. LOV gives me the available values. But how to set a default value upon Project Selection.

Thanks,

Vishnu