Tried it but the mentioned syntax is possible with only 2 selections. Anyways thanks Gilles!
But i got the solution,
The answer would be like we need to make the first selection in trigger as followed.
Select in field: Field name & in Search String Field1 Value.
Toggle Field: Field Name & in Search String Field2 Value.
Toggle Field: Field Name & In Search String Field3 Value.
Toggle Field: Field Name & in Search String Filedn Value.
Lock Field: Field Name.
Hope some one might get help from this.