this code designs a button that goes forward, how do I go to the previous?

1 reference private void BtnNext_Click(object sender, EventArgs e) \{ II retrieve the current position var currentPosition = int. Parse(this. txtRow. Text); I/retrieve the number of rows in the excel document var rowCount = this.persister. CountRows ( ) l/ignore attempts to go past the last row if (currentposition >= rowcount) \{ // do nothing else //advance to the next row and display it \{ If assign the column data from this row to each of the text boxes