Find as you type for a variable

I have a variable called ProjectName on a page 50000 which is of length text 250 and and this variable has a lookup to a field on Sales header table called Project Name but Project Name in Sales header table is not part of any key in Sales header table. I can create Project name as secondary key in Sales header table which I tried and also I tried to define Project Name field on the Sales header table as part of the Key group.

Is there any way on Page 50000 when user tries to enter value in variable ProjectName to search as they type to narrow down their choice to the typed value, basically what they are looking for something along the line of Sell-to customer no. where you can enter the customer no. and based on key group it filters the search for you, unfortunately Project name in my case is not primary key of Sales header table.

Any help is highly appreciated.

Thanks
RJ.