'Add these Code to correspoding button click event
' To add (+)
Me.lblAnswer.Text = iif(trim(txtBox1.text)="",0,Val(txtBox1.text)) + iif(trim(txtBox2.text)="",0,Val(txtBox2.text))
' To Subtract (-)
Me.lblAnswer.Text = iif(trim(txtBox1.text)="",0,Val(txtBox1.text)) - iif(trim(txtBox2.text)="",0,Val(txtBox2.text))

' To Multiply (*)
Me.lblAnswer.Text = iif(trim(txtBox1.text)="",0,Val(txtBox1.text)) * iif(trim(txtBox2.text)="",0,Val(txtBox2.text))

' To Devide (/)
Me.lblAnswer.Text = iif(trim(txtBox1.text)="",0,Val(txtBox1.text)) / iif(trim(txtBox2.text)="",0,Val(txtBox2.text))

Hope this solves your problem, Good Luck