how to install Opensuse on to a partition without it affecting grub installed by ubuntu

I have installed winxp then ubuntu I have made a primary partition of 20gb for Opensuse. When i booted the opensuse live cd partitioner suggests to delete the ubuntu root partition and recommends creating a home partition on the 20gb primary partition. if i choose to install opensuse custom and expert mode. i tried to install it in the primary partition for windows i selected to install the grub on to the primary partition it wiped of grub of ubuntu and installed opensuse grub. my question is the primary partition made for opensuse is 20gb. dev/sda3 if i install opensuse into this partion will the opensuse grub remove the ubuntu grub which has access to windows.?

In the installer you have the option of putting the openSUSE boot block on the partition boot record. In this place, it will not overwrite Ubuntu’s boot record which is in the MBR.