Simple VBA: Copy cell data from the top row in below cells (in the respective column)

[tyavan]

VBA: Copy cell data from the top row in below cells (in the respective column) with ":" sign if the cell is empty.
Say B1 data is x1* and C1 is empty then the empty cell data will become ":x1*"
Say G1 data is xx1* and G11 is empty then the empty cell data will become ":xx1*"
If the top row cell is not empty do nothing. Sheet name is given in VBA code "SheetX" because there are other sheets.