void SelectBlock(wxTextChunk * block, Bool select = TRUE)
void SelectBlock(long blockId, Bool select = TRUE)
If select is TRUE, select the existing block, marking it in cyan (colour screens) or in inverse video (monochrome screens). If select is FALSE, deselect the block. The first form is more efficient since no search need be done for the block.
Note that Compile must be called before this call has any visible effect.