Display Saved value of item in Dropdown

Question

Dear all
1)I have created Group Table (grp_id,Grp_Name) where iam storing group like 'Nokia,Samsung' etc
2)then i have created Product Master(pid,ProductName,grp_id,rate)
In Product Master form i have use Displaymemeber & valuemember property of combo box which display Grp_Name & grp_id in combobox from Group Master table.

When iam saving data to Product Master, it save like this:

Pid  ProductName grp_id rate
1     Nokia1100       1     1200
2   Nokia1000         1     1500
3   Samsung3500     2     2000

Till it is ok.
My problem occurs when displaying record.
It doesn't fectch groupNam on form. i know that iam not saving Groupname.
But can i show groupname in Combobox at the time of editing record Same as when i loading form.

Plz help me out!!!!!!!