Good habits are best established early in programming (as in life!)
I haven't changed your actual code at all but look how the use of tabs to indent lines reveals the structure in the code and makes it easier to read, particularly when you have nested constructs like Sub/End Sub, If/End If, For/Next, Do/While. You can adjust the amount of indent in the IDE for each tab character by Tools -> IDE Options -> TabSize
Code:
Sub headortail
a=ComboBox1.Text
b = TextBox1.Text
c = Num1.Text
e=Cos(((a*10)-b)*(22/(7*180)))*c
If Round(e)<0 Then
Label11.FontColor= cRed
Label2.FontColor= cRed
Return "TAIL"
Else If Round(e)=0 Then
Return " "
Else
Label11.FontColor= cBlack
Label2.FontColor= cBlack
Return "HEAD"
End If
End Sub
Another tip. Unless you need to return a string with a space character as in the code above you can just use Return on it's own which does in fact return an empty string.