// Shorten the object string, just for fewer typing:
o = document.selection;

// - - -

// Find something backwards/up, here empty line:
o.Find("^\\s*$",eeFindPrevious | eeFindReplaceRegExp);

// Remember the current line number:
yPosBegin = o.GetActivePointY(eePosLogical) +1;

// - - -

// Find again something downwards 
//   (here: find an blank line, non-greedy)
//   AND move the cursor that way to the found position :
o.Find("^\\s*$",eeFindNext | eeFindReplaceRegExp);

// Do an selection.
//   Set the start of the selection to the remembered line.
//   The end of the selection will be the current line:
o.SetAnchorPoint(eePosLogical, 1, yPosBegin); 

o = document.selection;

//Remember the current line number:
yPos = o.GetActivePointY( eePosLogical );

//Move cursor to found position (here: find an blank line):
o.Find("^$",eeFindNext | eeFindReplaceRegExp);

//Do an selection.
//Set the start of the selection to the remembered line:
o.SetAnchorPoint( eePosLogical, 1, yPos );