Don't use LotusScript. @Formula is WAY more appropriate here (you might use LS in the buttons, but you don't need it in the fields)
You would want to ADD a field to the form called "Status".
The field would be ComputedWhenComposed, numeric with the formula: 1
Then you create an action button "Submit" (you could compute the label)
"Submit for "+@Select(Status;"Check":"Approval":"Take Ownership")
The button formula is:
FIELD Pending := @true;
FIELD Status := Status + 1;
@if(@Command([FileSave]);@Command([FileCloseWindow]);"")
In the POSTOPEN event you put:
@if(@IsDocBeingEdited;"";@Return);
FIELD Pending := @false;
Now you have your 4 fields; which are ALL computed:
@if(Pending=@True;@ThisValue;Status=1;@UserName;@ThisValue)
@if(Pending=@True;@ThisValue;Status=2;@UserName;@ThisValue)
@if(Pending=@True;@ThisValue;Status=3;@UserName;@ThisValue)
@if(Pending=@True;@ThisValue;Status=4;@UserName;@ThisValue)
You also could have a button that walks the chain backwards if it gets rejected. Follow the same logic.
Enjoy!