textbox1 * textbox2 = textbox3

hi
i have had this previously , but has completely gone think its age ,
i have a userform with numerous text boxes , some are copies so only interested in these 3
tbox1 * tbox2 - tbox 3 ,
as i entered £50 in tb1
entered 2in tb2
tb3 was populated automatically
have tried different versions of this got it once doin me head in now also have populated a userform with a combobox which works but for the life of me cannot get it to populate a textbox1 with data
the combo box pops with 500ton row a and textbox should pop with value in row e
any takers please
as per previous threads im 56 too and its showing have uploaded cranes it is code for userform 1 you will have to go to developer , vb , userform1 and code to view as not userform1.show till got it right
cheers colin

[Private Sub TextBox3_Change()
If TextBox1.Value = "" Then Exit Sub
If TextBox2.Value = "" Then Exit Sub
TextBox3.Value = CDbl(TextBox1.Value) * CDbl(TextBox2.Value)
End Sub]