Looking up tiles

Okay im having trouble working out the math of looking up a tile from a bitmap file. The bitmaps are all 32 by 32 and there can be any amount of tiles in them in any number of rows or columns. I plan on the function taking the number of columns and the number for the tile say 5. Then I should be able to find the screen coordinates in pixels of the tile. Tile one would have a top of 0 a bottom of 32 a left of 0 and a right of 32. It seems easy but im having trouble any ideas? or did i not explain it well enough.

visual basic code:

Dim TileWidth As Integer
Dim TileHeight As Integer
Dim ImageWidth As Single
Dim numTilesX As Integer
Dim X As Single
Dim Y As Single
Dim i As Long

TileWidth = 32
TileHeight = 32
ImageWidth = 128
numTilesX = ImageWidth / TileWidth
i = 9

X = (i Mod numTilesX) * TileWidth
Y = (i - X / TileWidth) / numTilesX * TileHeight

One quick question what is the i variable for and why is it set to 9? Also It must be a rectangle so would I just use the Y and X again but say add 1*32 to get the right or bottom edge of the tile?

"I plan on the function taking the number of columns and the number for the tile say 5."

The i variable is that number... I just used 9 instead...


I don't understand the other question. Try explaining again...

The other question was just that I need the rectangle for the texture in the image. The left top right and bottom of the image. So the first rectangle would be 0,0 for the top and left and 32 32 for the bottom and right.

X, Y = Upper left corner of the tile
X + TileWidth, Y + TileHeight = Bottom right corner of the tile