how add columns or create new table from different two tables power bi without relationship

Hi HpDp 
Thank you for posting your query in the Microsoft Fabric community.

Calculated tables have fixed data structures and do not adjust with filter changes. Using measures provides a flexible and responsive report that reflects real-time changes based on user selections. Instead of creating a calculated column in Table C that directly depends on the slicer's selection, I have implemented two measures that dynamically compute values based on the slicer selection.

Measure 1:
Selected_Discount = SELECTEDVALUE('Table B'[DISCOUNT_PERCENT], 0)

Measure 2:
Adjusted_Value =  

SUMX( 

    'Table A', 

    'Table A'[VALUE] * (1 - [Selected_Discount]/100) 

)

Created a Table Visual:

• Bring in ITEM CODE from Table A.
• For "Selected Discount," instead of showing it directly, you can use the measure - Selected_Discount.
• For adjusted value, use the measure - Adjusted_Value

Use the slicer to select different discount percentages. The Selected_Discount measure will update accordingly, and the Adjusted_Value should accurately reflect the adjusted values from Table A. Please refer to the screenshot below, and I have attached the pbix file for your reference.

If this helps then please Accept it as a solution and dropping a "Kudos" so other members can find it more easily.
Hope this works for you!
Thanks.

Thank You So much. Thats fantastic... I did not thought in this direction. Great.