Overview:
As a developer many times a small Java script can save a lot of code! I have seen a blog to assign Java script function to a field but that did not work for me when assigning with a field of table view. I have done some experiment and decided to share within the community. Please feel free to add your comment or / and experience. 
First Step:
Create a Iterator class (BSP Iterator not BOL Collection Iterator) by copying sample iterator class CL_UIF_BP_SAMPLE_ITERATOR
In CRM Web UI component .HTM page -> create a instance and assign to attribute iterator of CHTMLB: ConfigTable, for example below:
<chtmlb:configTable xml = "<%= lv_xml %>"
iterator = "<%= gr_iterator %>"
Second Step:
In new BSP Iterator class redefine RENDER_CELL_START method to add Java script function to specific columns, for example below:
1. testFunction (rememeber Javascript function is case sensitive!) returns a message & prevent writing
and 2. testFunctionwithoutmessage does not return but prevent writing (Keydown)
DATA: lr_input TYPE REF TO cl_thtmlb_inputfield.
CASE p_tableview_id.
WHEN OTHERS.
CASE p_column_key.
WHEN 'ZZTEST'.
* No manual entry is allowed, only through search help
lr_input ?= p_replacement_bee.
lr_input->onkeydown = 'return testFunction()'.
p_replacement_bee ?= lr_input.
WHEN 'ZZTEST2.
* No manual entry is allowed, automatic through search help assignment
lr_input ?= p_replacement_bee.
lr_input->onkeydown = 'return testFunctionwithoutmessage()'.
p_replacement_bee ?= lr_input.
ENDCASE.
ENDCASE.
Third Step:
Write Javascript functions in .HTM page, for example below
<script type="text/javascript">
function myFunction() {
alert("Please select.");
return false;
}
function testFunctionwithoutmessage() {
return false;
}
</script>
Summary:
There is another method OnClientClick which is also useful. For my requirement these two served the purpose and saved a lot of code and importantly server rendering. Have fun