How To Make A Correct Select

Could anyone help med with a select statement with a join between to
tables. It is to be used in a OLAP cube.
I Havde table LedgerBudget and Table Admin. In table admin I can setup
a from and to date and also a budgetmodel.
The admin have ONE record per OLAP cube.

The statement below works fine if I have stated a budgetmodel in table
Admin.
But if no budetmodel stated in table Admin, I want the statement to
select every ledgerbudget with active = 1 and allocatemethod = 0
Could anyone help me with this.


SELECT LTRIM(dbo.LEDGERBUDGET.ACCOUNTNUM) AS ACCOUNT_ID,
dbo.LEDGERBUDGET.STARTDATE AS TRANSDATE, - dbo.LEDGERBUDGET.AMOUNT AS
BUDGET
FROM dbo.LEDGERBUDGET INNER JOIN
dbo.ADMIN ON dbo.LEDGERBUDGET.STARTDATE >=
dbo.ADMIN.FROMDATE AND
dbo.LEDGERBUDGET.STARTDATE <= dbo.ADMIN.TODATE
AND
dbo.LEDGERBUDGET.MODELNUM =
dbo.ADMIN.BUDGETMODELID
WHERE (dbo.LEDGERBUDGET.ACTIVE = 1) AND
(dbo.LEDGERBUDGET.ALLOCATEMETHOD = 0)


BR/Thanks