Well, the math behind it is simple enough.
Dim X1 As Float = 123 'left
Dim X2 As Float = 987 'right
Dim Y1 As Float = 135 'top
Dim Y2 As Float = 357 'bottom
Dim T1 As Float = 5 * 60 + 27 'eg time-of-day in minutes
Dim T2 As Float = 19 * 60 + 41
and then you just need something to calculate the X and Y of the sun position or path at time T
Dim P As Float = (T - T1) / (T2 - T1) 'P is proportion 0..half..1 of T within time range T1..midday..T2
Dim X As Float = X1 + P * (X2 - X1)
Dim Y As Float = Y2 + SinD(P * 180) * (Y1 - Y2) 'shape good enough; if you really need a circular arc, it can be done with a bit more math
so all you have to do now is put coloured pixels at those locations... how hard could that be?!?!
A starting point might be to make a small square panel to represent your sun (background = yellow) and set the corner radius sufficiently large to turn the square into a circle (or somewhere in between, to make your app more memorable ;-) You can then move the sun about by changing the panel's Left and Top (aka X and Y) properties.