@ http://www.crystalreportsbook.com/Forum/member_profile.asp?PF=3327&FID=8 - lockwelle : thanks, but can you explain a bit more. I dont seem to get you too well. Where do I then store the parameter? and do I call it in the select expert?

Multi-valued parameters return arrays, not strings, so you can't compare them to strings.  Instead, you have to use some of the array functions.  Also, your Switch statement is not going to get you all of the values - it only evaluates until the first time it hits a "True" expression.

Stringvar Array filter := ['default'];
local Numbervar j;
local Numbervar items := 0;
local Booleanvar isAll := false;
for j := 1 to Ubound({?Department} Do
(
  if not isAll then
  (
    if {?Department}[j] = 'All Departments' then
    (
      isAll := true;
      filter := ['', 'JOB - EXT', 'JOB-AFMEXP', 'JOB-LUB/S', 'JOB-NBCMTU',
      'JOB_ABB_AS', 'JOB-CANPJB', 'JOB_INSTAL', 'JOB_CUMNS', 
      'JOB-W/SHOP', 'JOB-WS/GEN', 'JOB-WTY', 'JOB-MAR', 'JOB-S/AGR', 
      'RENTAL'];
    )
    if {?Department}[j] = 'Project' then
    (
      items := items + 1;
      redim filter [items];
      filter[items] := 'JOB-INSTAL';
    )
    if {?Department}[j] = 'Field Service' then
    (
      items := items + 5;
      redim filter[items];
      filter[items - 4] := 'JOB-EXT';
      filter[items - 3] := 'JOB-AFMEXP';
      filter[items - 2] := 'JOB-LUB/S';
      filter[items - 1] := 'JOB-NBCMTU';
      filter[items] := 'JOB-ABB-AS';
    )
     <etc... through all of your department values>
  )    
 )
filter