Add blank characters to end of cell so all values total 20 characters

I have a column of data that isn't always the same length. I need blank spaces added to the end of the data so the total number of characters is always 20.

Example:

A1:ValueABC
A2:ValueDEFGHI
A3:ValueJ
A4:ValueKLMNOPQRSTUVWXY

Is there a formula that could make values in B as such:

ValueABC____________
ValueDEFGHI_________
ValueJ______________
ValueKLMNOPQRSTUVWXY

Thanks in advance.

Try =A1&REPT("_",20-LEN(A1))

.....slightly different version

=LEFT(A1&REPT("_",20),20)

If A1 has more than 20 characters that also truncates to 20