inserting a blank column and copy values

Dear All,

I have to write a macro for the following requirements.

1. I want to insert a blank column in a working sheet. It should be the column A or first column in every sheet.

2. Then A1 has to filled with text "Date"

3. A combo box with " Which date u would like to insert" , if i will give any date then it should copy across the values in the A column ( i want to copy the date till the cells where the adjacent B column values finishes)

I have enclosed a sample copy for your reference, where i have highlighted with the yellow color.

I have huge data to format in this way. If you are kind enough to guide me, i will be grateful to you for your help.

With sincere regards,
Upananda