How to set current datasource in a form?

Hi Guys,

I have an issue in a form, wherein I have multiple datasources and each datasource is displayed in a grid in each tab page. When I go to Tab3 (not selecting the grid in this case) then create a new record (Ctrl + N), the cursor goes to DS1 - Tab1 - Grid1. How do I set DS3 as the current datasource when I go to Tab3? Though selecting Grid3 sets DS3 as the current datasource but I want it upon selection of Tab3 instead.

DS1 - Tab1 - Grid1

DS2 - Tab2 - Grid2

DS3 - Tab3 - Grid3

Thanks,

Paul