It's possible, but it requires using dynamic SQL.
I recommend reading The curse and blessings of dynamic SQL before continuing...
DECLARE @theDate varchar(60)
SET @theDate = '''2010-01-01'' AND ''2010-08-31 23:59:59'''
DECLARE @SQL VARCHAR(MAX)
SET @SQL = 'SELECT AdministratorCode,
SUM(Total) as theTotal,
SUM(WOD.Quantity) as theQty,
AVG(Total) as avgTotal,
(SELECT SUM(tblWOD.Amount)
FROM tblWOD
JOIN tblWO on tblWOD.OrderID = tblWO.ID
WHERE tblWO.Approved = ''1''
AND tblWO.AdministratorCode = tblWO.AdministratorCode
AND tblWO.OrderDate BETWEEN '+ @theDate +')'
EXEC(@SQL)
Dynamic SQL is just a SQL statement, composed as a string before being executed. So the usual string concatenation occurs. Dynamic SQL is required whenever you want to do something in SQL syntax that isn't allowed, like:
EXEC sp_executesql allows you to use bind/preparedstatement parameters so you don't have to concern yourself with escaping single quotes/etc for SQL injection attacks.