Loop Macro. Prompt Input.

I have several hundred workbooks with multiple worksheets(15-35) that I am trying to tidy up, so the data can be entered into a database. Its my first attempt at VBA and between the forum and macro recorder I made an attempt which is below. I just can't seem to get over the last part. I have searched the forum but can't seem to find any relevant information. I have a couple of questions.

1. I need to be able to run this macro over all the worksheets in the workbook, so how can I loop it? All the worksheets are named differently i.e. peoples names.

2. In my code I have inserted 4 columns. These columns will be the only thing common between all the worksheets. A1 to A30 = Week number, B1 to B30 = Shift Number, C1 to C30 = Supervisor number. Column D is blank. I'd like to be able to be prompted to enter these 3 numbers at the start if possible? Can this be done in such a way as you are only prompted the once and not on each worksheet? I picked 30 rows because the amount of rows in each worksheet varies but never exceeds this. The end of my code "Delete rows where cell B is blank" will delete any excess data where 30 rows of week numbers etc are not needed.

Sub CleanCost1_1()
'
' CleanCost1_1 Macro
' Macro recorded 04/09/2009
'

' Delete Job Card Sheet
Sheets("Job Card").Select
Application.DisplayAlerts = False
ActiveSheet.Delete
Application.DisplayAlerts = True
' Delete Master Sheet