Thanks Ahmad for your interest in my problem.
the c code is from KACST ,I got it from this link:
from their FAQ page:
and I think there is no problem regarding the permission because it is for all muslims around the world.
Regarding your question either converting it to DLL or porting to VB, what I want is to get the prayer times in visual basic as functions so that I can do the interface easily.
I have no idea at all about converting the c code to DLL and the way to use it in VB. Of course I prefer converting it from c to VB because this is the only way I can play with the code inside VB.
Thanks Ahmad again for your help, and waiting for your response Wa Gazak Allah Kair.