Scroll Word's font size selector
Word VBA, 199 147 126 116 102 100 87 85  Bytes

Why emulate when you can do?!
Declared function in the ThisDocument module that takes input n in the form of Array(true,true,false,true) and outputs to the Word font size selector :P
Golfed:
Sub a(n):Set f=Content.Font:For Each i In n
If i Then f.Grow Else f.Shrink
Next:End Sub

Ungolfed:
Sub a(n)
    Set f=ThisDocument.Content.Font
    For Each i In n
        If i Then 
            f.Grow 
        Else 
            f.Shrink
        End if 
    Next
    ''  Implicitly output font size to MS Word Font Size Selector 
End Sub

.GIF of usage

Thanks
-21 thanks to @Adám (removed Selection.WholeStory: call)
-10 thanks to @Adám (assume clean environment; remove f.size=11: call)
-14 thanks to @Adám (cheeky output word font size selector)
-2 thanks to @Adám (bool ParamArray)
-13 for changing ParamArray n() to n and expecting input as Boolean Array
-2 for moving from a code module to the ThisDocument module
Old Version 114 Bytes
Takes input n as a ParamArray, in the form of true,true,false,true and outputs word vbe immediates window
Sub a(ParamArray n()):Set f=Selection.Font:For Each i In n
If i Then f.Grow Else f.Shrink
Next:Debug.?f.Size:End Sub

Older version, 199 Bytes
Takes input in the form of 170,-4,6,-1 (accepts numbers larger than 1 in magnitude)
Sub a(ParamArray n()):Selection.WholeStory:Set f=Selection.Font:f.Size=12:For Each i In n
If i&gt;1 Then
For j=i To 0 Step -1:f.Grow:Next
Else
For j=i To 0:f.Shrink:Next:End If:Next:Debug.?f.Size:End Sub