Apply underline a text formatting

[bacdh52]

hello
i have issue with mail merge. after mail merge


I have a table as bellow

Category Data Spec
name 1 80 90~100
name 2 90 90~100
name 3 100 90~100
name 4 110 90~100
name 5 70 90~100

With data outspec, I want underline text as

Category Data Spec
name 1 80 90~100
name 2 90 90~100
name 3 100 90~100
name 4 110 90~100
name 5 70 90~100

Please help me
thank you very much