Subreport Field Linker

[Walter]

I have a query that my main report is based upon and then I have inserted a
graph which runs off of a SQL query. However, I want the graph to change
based upon the LastName field but it won't allow me to do that. I keep
getting the following dialog box when I try to link child to master: "Can't
build a link between unbound forms." Even if I put in "LastName" for the
child and Master links, the report then comes out blank.

Main Query:
SELECT tblManager.ManagerName, tblProcurementAgent.LastName,
tblContract.EffectiveDate, tblContract.ExpirationDate, tblContract.MaxROLT,
[ExpirationDate]-[MaxROLT] AS [Contract Award Due],
tblContract.LegalContractStatus, tblContract.LegalContractNumber,
tblContract.SupplierName, [ExpirationDate]-[MaxROLT]-365 AS [Start Board
(min)]
FROM tblContract LEFT JOIN (tblProcurementAgent LEFT JOIN tblManager ON
tblProcurementAgent.Budget = tblManager.Budget) ON tblContract.PAFocal =
tblProcurementAgent.BuyerCode
GROUP BY tblManager.ManagerName, tblProcurementAgent.LastName,
tblContract.EffectiveDate, tblContract.ExpirationDate, tblContract.MaxROLT,
[ExpirationDate]-[MaxROLT], tblContract.LegalContractStatus,
tblContract.LegalContractNumber, tblContract.SupplierName,
[ExpirationDate]-[MaxROLT]-365
HAVING (((tblManager.ManagerName)="manager1" Or
(tblManager.ManagerName)="manager2") AND
((tblContract.ExpirationDate)>=Date()));

Secondary Query:
SELECT QryStartPB.SupplierName, QryStartPB.[Start Board (min)],
QryStartPB.ManagerName, QryStartPB.LastName
FROM QryStartPB
GROUP BY QryStartPB.SupplierName, QryStartPB.[Start Board (min)],
QryStartPB.ManagerName, QryStartPB.LastName
ORDER BY QryStartPB.[Start Board (min)] DESC;