I have little experience with chip-seq data and I am trying to determine the proximity of histone Chip-seq peaks to nearby genes. I am working with narrowpeak bed files from public histone chip-seq datasets. I want to take the reads and map them to a 2000 bp region surrounding the TSSs of genes defined by a Refseq gene annotation file. I then want to sum the number of tags mapped to a specific TSS. How would I go about doing this?