Coding problem please help.

hi there, I've run into a problem that I am unable to fix and need some help because I am a beginner. Basically ive been running a code for form filling that allows the correct option box to apply an "x" onto the form and its worked fine for previous forms, however on this form using the exact same code I run into "runtime error 438" with this piece of code highlighted in yellow, Sheets(2).Range("E63").Value = "x"
This is the full code I've been using

Private Sub CommandButton2_Click()
If Unit151.Frame6.OptionButton16.Value Then
Sheets(2).Range("E63").Value = "x"
ElseIf Unit151.Frame6.OptionButton17.Value = True Then
Sheets(2).Range("F63").Value = "x"
Else
Sheets(2).Range("G63").Value = "x"
End If
End Sub

Any help or suggestions would be helpful thank you.