Since I have found a solution, i'll share:
The workaround is by concatenating all field values into one field using a qualifier like # between the values, in the LOAD script. This creates a unique value for each row. Then reading only this value to vbscript using ActiveDocument.Fields("unique").GetPossibleValues(20000) and then breaking it down to the former values.
I used the Split fucntion to break down the values to an array.