Thanks so much for helping out. I will use the syntax posted in the solution.
Here is the part that I had needed help with in my where clause...
(where (timesheet.wcstart between @start_date and @end_date and timesheet.wcfinish is null))
INSERT INTO #timesheet
SELECT emp.firstname + ' ' + emp.surname, mo.monumber, inv.customer_part_num, inv.description, t.opno, routing.description,workcenter.name,
Case When timesheet.wcstart < @start_date then @start_date
Else timesheet.wcstart
End,
timesheet.wcfinish,
ISNULL(workcenter.machine,'X'),
'',
TSNo
FROM mfg_timesheet t
Left outer join cubs..mfg_mo_routing routing On
routing.companyid = timesheet.companyid and
routing.mo_key = timesheet.mo_key and
routing.opno = timesheet.opno
Left outer join cubs..mfg_workcenter workcenter On
workcenter.wcno = timesheet.wcno and
workcenter.companyid = timesheet.companyid,
mfg_mo mo, inv_item inv,mfg_employee emp,slsord sls
where (timesheet.wcstart between @start_date and @end_date and timesheet.wcfinish is null) and
mo.mo_key = timesheet.mo_key and
emp.employeeid = timesheet.employeeid and
mo.companyid = inv.company_id and
mo.stocknumber = inv.stock_number and
timesheet.companyid = 1 and
workcenter.machine IN ('W') And
TSNo NOT IN (SELECT TsNo FROM mfg_timesheetAdj) and
sls.company_id = mo.companyid and
sls.slsord_number = mo.slsord_number